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, 7 insertions, 1 deletions

diff --git a/main/wifistr.c b/main/wifistr.c
index bf03b4d..543aaf6 100644
--- a/main/wifistr.c
+++ b/main/wifistr.c
@@ -2,6 +2,7 @@
 #include "identity.h"
 #include "nostr_event.h"
 #include "config.h"
+#include "local_relay.h"
 #include "esp_log.h"
 #include "esp_tls.h"
 #include "esp_crt_bundle.h"
@@ -216,8 +217,13 @@ esp_err_t wifistr_publish(void)
 
     ESP_LOGI(TAG, "Wifistr event: %s", event_json);
 
+    esp_err_t local_ret = local_relay_publish(event_json, strlen(event_json));
+    if (local_ret == ESP_OK) {
+        ESP_LOGI(TAG, "Published to local relay");
+    }
+
     const tollgate_config_t *cfg = tollgate_config_get();
-    esp_err_t last_err = ESP_FAIL;
+    esp_err_t last_err = local_ret;
 
     for (int i = 0; i < cfg->nostr_relay_count; i++) {
         esp_err_t err = ws_send_to_relay(cfg->nostr_relays[i], event_json);