feat: local Nostr relay with relay selection, sync, and integration tests

Local Nostr relay (NIP-01) on port 4869 with LittleFS 4MB storage.
All events published locally first, then synced to public relays via REQ-diff.
Relay selection via NIP-11 HTTP probing with NIP-77 scoring and auto-failover.

Components:
- wisp_relay: 16-file local relay (ws_server, storage_engine, sub_manager,
  broadcaster, relay_validator, router, handlers, rate_limiter, nip11,
  deletion, flash_monitor, relay_types)
- esp_littlefs: LittleFS VFS integration (git submodule)
- negentropy: for future NIP-77 binary sync (git submodule)

New source files:
- local_relay.c/h: thin wrapper for relay init/start/publish
- relay_selector.c/h: NIP-11 probe + scoring + auto-failover
- sync_manager.c/h: REQ-diff sync (primary 30min, fallback 6h)

Bug fixes:
- config.c: use-after-free (cJSON_Delete before seed_relays/sync parsing)
- local_relay: moved init to app_main for boot-time start (not gated on STA IP)

Flash layout: 4MB LittleFS partition at 0x500000 for relay_store

Test results (Board B, live hardware):
- Smoke: ping + HTTP 4869 + NIP-11: PASS
- NIP-11 info document: 10/11 PASS
- WS pub/sub (connect, REQ/EOSE, EVENT/OK, CLOSE, concurrent): 6/6 PASS
- Unit tests (relay_validator + relay_selector): 13/13 PASS

Hardware test make targets in physical-router-test-automation/:
- make relay-build, relay-flash-b, relay-test-smoke/nip11/pubsub/sync/full

1 files changed, 92 insertions, 0 deletions

diff --git a/components/wisp_relay/sub_manager.h b/components/wisp_relay/sub_manager.h
new file mode 100644
index 0000000..64afb04
--- /dev/null
+++ b/components/wisp_relay/sub_manager.h
@@ -0,0 +1,92 @@
+#ifndef SUB_MANAGER_H
+#define SUB_MANAGER_H
+
+#include <stdbool.h>
+#include <stdint.h>
+#include "esp_err.h"
+#include "freertos/FreeRTOS.h"
+#include "freertos/semphr.h"
+#include "relay_types.h"
+
+#define SUB_MAX_TOTAL         64
+#define SUB_MAX_PER_CONN      8
+#define SUB_MAX_FILTERS       4
+#define SUB_MAX_ID_LEN        64
+
+#define SUB_MAX_FILTER_IDS    20
+#define SUB_MAX_FILTER_AUTHORS 20
+#define SUB_MAX_FILTER_KINDS  20
+#define SUB_MAX_FILTER_ETAGS  20
+#define SUB_MAX_FILTER_PTAGS  20
+
+typedef enum {
+    SUB_OK = 0,
+    SUB_ERR_INVALID,
+    SUB_ERR_TOO_MANY_FILTERS,
+    SUB_ERR_MEMORY,
+    SUB_ERR_NOT_FOUND,
+} sub_error_t;
+
+typedef struct {
+    char *ids[SUB_MAX_FILTER_IDS];
+    size_t ids_count;
+    char *authors[SUB_MAX_FILTER_AUTHORS];
+    size_t authors_count;
+    int32_t kinds[SUB_MAX_FILTER_KINDS];
+    size_t kinds_count;
+    char *e_tags[SUB_MAX_FILTER_ETAGS];
+    size_t e_tags_count;
+    char *p_tags[SUB_MAX_FILTER_PTAGS];
+    size_t p_tags_count;
+    int64_t since;
+    int64_t until;
+    int limit;
+} sub_filter_t;
+
+typedef struct {
+    char sub_id[SUB_MAX_ID_LEN + 1];
+    int conn_fd;
+    sub_filter_t filters[SUB_MAX_FILTERS];
+    uint8_t filter_count;
+    uint16_t events_sent;
+    bool active;
+} subscription_t;
+
+typedef struct sub_manager {
+    subscription_t subs[SUB_MAX_TOTAL];
+    SemaphoreHandle_t lock;
+    uint16_t active_count;
+} sub_manager_t;
+
+typedef struct {
+    int conn_fd;
+    char sub_id[SUB_MAX_ID_LEN + 1];
+} sub_match_entry_t;
+
+typedef struct {
+    sub_match_entry_t matches[SUB_MAX_TOTAL];
+    uint8_t count;
+} sub_match_result_t;
+
+esp_err_t sub_manager_init(sub_manager_t *mgr);
+void sub_manager_destroy(sub_manager_t *mgr);
+
+sub_error_t sub_manager_add(sub_manager_t *mgr, int conn_fd,
+                            const char *sub_id,
+                            const sub_filter_t *filters,
+                            size_t filter_count);
+
+sub_error_t sub_manager_remove(sub_manager_t *mgr, int conn_fd,
+                               const char *sub_id);
+
+void sub_manager_remove_all(sub_manager_t *mgr, int conn_fd);
+
+void sub_manager_match_json(sub_manager_t *mgr, const char *event_json,
+                            size_t event_len, int event_kind,
+                            const char *event_pubkey_hex,
+                            uint64_t event_created_at,
+                            sub_match_result_t *result);
+
+uint8_t sub_manager_count(sub_manager_t *mgr, int conn_fd);
+
+#endif