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, 6 insertions, 0 deletions

diff --git a/main/config.h b/main/config.h
index fa4d95c..1e580e9 100644
--- a/main/config.h
+++ b/main/config.h
@@ -13,6 +13,7 @@
 #define TOLLGATE_MAX_AP_SSID_LEN   32
 #define TOLLGATE_MAX_AP_PASS_LEN   64
 #define TOLLGATE_MAX_RELAYS        4
+#define TOLLGATE_MAX_SEED_RELAYS   8
 
 typedef struct {
     char ssid[32];
@@ -63,6 +64,11 @@ typedef struct {
 
     bool cvm_enabled;
     char cvm_relays[256];
+
+    char nostr_seed_relays[TOLLGATE_MAX_SEED_RELAYS][128];
+    int nostr_seed_relay_count;
+    int nostr_sync_interval_s;
+    int nostr_fallback_sync_interval_s;
 } tollgate_config_t;
 
 void tollgate_config_derive_unique(tollgate_config_t *cfg);