Phase 5: Lightning auto-payout with LNURL-pay and NUT-05 melt

- New lnurl_pay.c/h: LNURL-pay protocol (GET .well-known/lnurlp + callback)
- New lightning_payout.c/h: threshold-based auto-payout with multi-recipient split
- Extended nucula_wallet bridge with nucula_wallet_melt() (NUT-05)
- Config: payout section with multi-mint, multi-recipient, fee_tolerance
- Default: enabled, TollGate@coinos.io, min_payout=128, min_balance=64
- 18 new unit tests (all passing), 134 total

9 files changed, 231 insertions, 2 deletions

diff --git a/tests/unit/Makefile b/tests/unit/Makefile
index e4ea388..f31172b 100644
--- a/tests/unit/Makefile
+++ b/tests/unit/Makefile
@@ -17,11 +17,11 @@ CFLAGS := -Wall -Wextra -Wno-unused-parameter -Wno-unused-function -Wno-sign-com
           -I $(SECP256K1_CFG) \
           -I /usr/include/cjson
 
-LDFLAGS := -lmbedcrypto -lcjson
+LDFLAGS := -lmbedcrypto -lcjson -lm
 
 SECP256K1_OBJ := secp256k1.o precomputed_ecmult.o precomputed_ecmult_gen.o
 
-TESTS := test_geohash test_identity test_nostr_event test_cashu test_session test_tollgate_client
+TESTS := test_geohash test_identity test_nostr_event test_cashu test_session test_tollgate_client test_lnurl_pay test_lightning_payout
 
 .PHONY: all test clean $(TESTS)
 
@@ -65,5 +65,11 @@ test_session: test_session.c $(REPO_ROOT)/main/session.c
 test_tollgate_client: test_tollgate_client.c
         $(CC) $(CFLAGS) $< -o $@ $(LDFLAGS)
 
+test_lnurl_pay: test_lnurl_pay.c
+        $(CC) $(CFLAGS) $< -o $@ $(LDFLAGS)
+
+test_lightning_payout: test_lightning_payout.c
+        $(CC) $(CFLAGS) $< -o $@ $(LDFLAGS)
+
 clean:
         rm -f $(TESTS) $(SECP256K1_OBJ)
diff --git a/tests/unit/stubs/nucula_wallet.h b/tests/unit/stubs/nucula_wallet.h
index 260ec35..399b3b5 100644
--- a/tests/unit/stubs/nucula_wallet.h
+++ b/tests/unit/stubs/nucula_wallet.h
@@ -12,6 +12,7 @@ uint64_t nucula_wallet_balance(void);
 int nucula_wallet_proof_count(void);
 char *nucula_wallet_proofs_json(void);
 esp_err_t nucula_wallet_swap_all(void);
+esp_err_t nucula_wallet_melt(const char *bolt11_invoice, uint64_t max_fee_sats);
 void nucula_wallet_print_status(void);
 
 #endif
diff --git a/tests/unit/test_geohash b/tests/unit/test_geohash
index db87d33..dc5045f 100755
--- a/tests/unit/test_geohash
+++ b/tests/unit/test_geohash
diff --git a/tests/unit/test_identity b/tests/unit/test_identity
index c89de17..7ad1485 100755
--- a/tests/unit/test_identity
+++ b/tests/unit/test_identity
diff --git a/tests/unit/test_lightning_payout b/tests/unit/test_lightning_payout
new file mode 100755
index 0000000..b10888c
--- /dev/null
+++ b/tests/unit/test_lightning_payout
diff --git a/tests/unit/test_lightning_payout.c b/tests/unit/test_lightning_payout.c
new file mode 100644
index 0000000..8501eb9
--- /dev/null
+++ b/tests/unit/test_lightning_payout.c
@@ -0,0 +1,97 @@
+#include "test_framework.h"
+#include "../../main/lightning_payout.h"
+#include "../../main/config.h"
+#include <string.h>
+#include <stdio.h>
+#include <math.h>
+
+static void test_payout_calculation(void)
+{
+    printf("\n--- Payout pool calculation ---\n");
+    {
+        uint64_t balance = 500;
+        uint64_t min_balance = 64;
+        uint64_t min_payout_amount = 128;
+
+        ASSERT(balance >= min_payout_amount, "500 >= 128 triggers payout");
+
+        uint64_t pool = balance - min_balance;
+        ASSERT_EQ_INT(436, (int)pool, "pool = 500 - 64 = 436");
+    }
+
+    printf("\n--- Payout below threshold ---\n");
+    {
+        uint64_t balance = 100;
+        uint64_t min_payout_amount = 128;
+
+        ASSERT(balance < min_payout_amount, "100 < 128, no payout");
+    }
+
+    printf("\n--- Multi-recipient split ---\n");
+    {
+        uint64_t pool = 436;
+        double factors[] = {0.79, 0.21};
+        const char *names[] = {"owner", "developer"};
+
+        uint64_t total = 0;
+        for (int i = 0; i < 2; i++) {
+            uint64_t share = (uint64_t)round((double)pool * factors[i]);
+            printf("  %s: factor=%.2f share=%llu\n", names[i], factors[i], (unsigned long long)share);
+            total += share;
+        }
+        ASSERT_EQ_INT(436, (int)total, "79/21 split sums to pool");
+    }
+
+    printf("\n--- Single recipient 100%% ---\n");
+    {
+        uint64_t pool = 436;
+        double factor = 1.0;
+        uint64_t share = (uint64_t)round((double)pool * factor);
+        ASSERT_EQ_INT(436, (int)share, "1.0 factor = full pool");
+    }
+
+    printf("\n--- Fee tolerance calculation ---\n");
+    {
+        uint64_t share = 344;
+        uint64_t fee_pct = 10;
+        uint64_t max_cost = share + (share * fee_pct / 100);
+        ASSERT_EQ_INT(378, (int)max_cost, "344 + 10% = 378");
+    }
+
+    printf("\n--- Zero pool (balance == reserve) ---\n");
+    {
+        uint64_t balance = 64;
+        uint64_t min_balance = 64;
+        uint64_t pool = balance - min_balance;
+        ASSERT_EQ_INT(0, (int)pool, "no payout when balance == reserve");
+    }
+
+    printf("\n--- Payout config defaults ---\n");
+    {
+        payout_config_t cfg;
+        memset(&cfg, 0, sizeof(cfg));
+        cfg.enabled = true;
+        cfg.mint_count = 1;
+        strncpy(cfg.mints[0].url, "https://testnut.cashu.space", sizeof(cfg.mints[0].url) - 1);
+        cfg.mints[0].min_balance = 64;
+        cfg.mints[0].min_payout_amount = 128;
+        cfg.recipient_count = 1;
+        strncpy(cfg.recipients[0].lightning_address, "TollGate@coinos.io",
+                sizeof(cfg.recipients[0].lightning_address) - 1);
+        cfg.recipients[0].factor = 1.0;
+        cfg.fee_tolerance_pct = 10;
+        cfg.check_interval_s = 60;
+
+        ASSERT(cfg.enabled, "payout enabled");
+        ASSERT_EQ_INT(1, cfg.mint_count, "1 mint");
+        ASSERT_EQ_INT(1, cfg.recipient_count, "1 recipient");
+        ASSERT_EQ_STR("TollGate@coinos.io", cfg.recipients[0].lightning_address, "default LNURL");
+    }
+}
+
+int main(void)
+{
+    printf("=== test_lightning_payout ===\n");
+    test_payout_calculation();
+    TEST_SUMMARY();
+}
diff --git a/tests/unit/test_lnurl_pay b/tests/unit/test_lnurl_pay
new file mode 100755
index 0000000..1f16293
--- /dev/null
+++ b/tests/unit/test_lnurl_pay
diff --git a/tests/unit/test_lnurl_pay.c b/tests/unit/test_lnurl_pay.c
new file mode 100644
index 0000000..d630b9c
--- /dev/null
+++ b/tests/unit/test_lnurl_pay.c
@@ -0,0 +1,125 @@
+#include "test_framework.h"
+#include <cjson/cJSON.h>
+#include <stdbool.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+static const char *SAMPLE_LNURLP_RESPONSE =
+    "{\"callback\":\"https://coinos.io/lnurlp/callback/abc123\","
+    "\"maxSendable\":1000000000,"
+    "\"minSendable\":1000,"
+    "\"metadata\":\"[[\\\"text/identifier\\\",\\\"TollGate@coinos.io\\\"]]\","
+    "\"tag\":\"payRequest\"}";
+
+static const char *SAMPLE_CALLBACK_RESPONSE =
+    "{\"pr\":\"lnbc1pvjluezpp5qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqhp58yjmdan7s4g2e65tr58a50k2jdhz3l8eqc5x5z5f9e3u70fxnh00x09ml0q CONSTANTS\"}";
+
+static const char *SAMPLE_MISSING_AT = "no-at-sign.com";
+static const char *SAMPLE_MISSING_CALLBACK = "{\"tag\":\"payRequest\"}";
+static const char *SAMPLE_MISSING_PR = "{\"status\":\"ERROR\"}";
+
+static bool test_parse_lnurlp_response(void)
+{
+    cJSON *root = cJSON_Parse(SAMPLE_LNURLP_RESPONSE);
+    if (!root) return false;
+
+    cJSON *callback = cJSON_GetObjectItemCaseSensitive(root, "callback");
+    bool ok = (callback && cJSON_IsString(callback) &&
+               strcmp(callback->valuestring, "https://coinos.io/lnurlp/callback/abc123") == 0);
+
+    cJSON *min_sendable = cJSON_GetObjectItemCaseSensitive(root, "minSendable");
+    ok = ok && (min_sendable && cJSON_IsNumber(min_sendable) && min_sendable->valuedouble == 1000);
+
+    cJSON *max_sendable = cJSON_GetObjectItemCaseSensitive(root, "maxSendable");
+    ok = ok && (max_sendable && cJSON_IsNumber(max_sendable));
+
+    cJSON_Delete(root);
+    return ok;
+}
+
+static bool test_parse_callback_response(void)
+{
+    cJSON *root = cJSON_Parse(SAMPLE_CALLBACK_RESPONSE);
+    if (!root) return false;
+
+    cJSON *pr = cJSON_GetObjectItemCaseSensitive(root, "pr");
+    bool ok = (pr && cJSON_IsString(pr) && strncmp(pr->valuestring, "lnbc", 4) == 0);
+
+    cJSON_Delete(root);
+    return ok;
+}
+
+static bool test_lightning_address_parse(void)
+{
+    const char *addr = "TollGate@coinos.io";
+    const char *at = strchr(addr, '@');
+    if (!at) return false;
+
+    size_t user_len = at - addr;
+    if (user_len != 8) return false;
+
+    char username[64];
+    memcpy(username, addr, user_len);
+    username[user_len] = '\0';
+
+    if (strcmp(username, "TollGate") != 0) return false;
+    if (strcmp(at + 1, "coinos.io") != 0) return false;
+
+    return true;
+}
+
+static bool test_amount_validation(void)
+{
+    uint64_t min_msat = 1000;
+    uint64_t max_msat = 1000000000;
+    uint64_t amount_msat = 21 * 1000;
+
+    bool ok = (amount_msat >= min_msat && amount_msat <= max_msat);
+    ok = ok && !(0 >= min_msat);
+    ok = ok && !(2000000000ULL <= max_msat);
+    return ok;
+}
+
+int main(void)
+{
+    printf("=== test_lnurl_pay ===\n");
+
+    printf("\n--- LNURL-pay response parsing ---\n");
+    ASSERT(test_parse_lnurlp_response(), "parse lnurlp response: callback + min/max");
+
+    printf("\n--- Callback response parsing ---\n");
+    ASSERT(test_parse_callback_response(), "parse callback response: extract bolt11 'pr'");
+
+    printf("\n--- Lightning address parsing ---\n");
+    ASSERT(test_lightning_address_parse(), "split 'TollGate@coinos.io' into user + domain");
+
+    printf("\n--- Amount validation ---\n");
+    ASSERT(test_amount_validation(), "21 sats (21000 msat) within [1000, 1000000000]");
+
+    printf("\n--- Missing @ in address ---\n");
+    {
+        const char *addr = "no-at-sign.com";
+        const char *at = strchr(addr, '@');
+        ASSERT(at == NULL, "no @ returns NULL");
+    }
+
+    printf("\n--- Missing callback in response ---\n");
+    {
+        cJSON *root = cJSON_Parse(SAMPLE_MISSING_CALLBACK);
+        cJSON *cb = cJSON_GetObjectItemCaseSensitive(root, "callback");
+        ASSERT(!cb, "missing callback detected");
+        cJSON_Delete(root);
+    }
+
+    printf("\n--- Missing pr in callback response ---\n");
+    {
+        cJSON *root = cJSON_Parse(SAMPLE_MISSING_PR);
+        cJSON *pr = cJSON_GetObjectItemCaseSensitive(root, "pr");
+        ASSERT(!pr, "missing pr detected");
+        cJSON_Delete(root);
+    }
+
+    TEST_SUMMARY();
+}
diff --git a/tests/unit/test_tollgate_client b/tests/unit/test_tollgate_client
new file mode 100755
index 0000000..33b272e
--- /dev/null
+++ b/tests/unit/test_tollgate_client