etcp_router: Ed25519 digital signature for service messages

- Add ed25519_public_key[32] to NODEINFO struct for pubkey distribution
- Add ed25519_public_key[32] to ROUTE_BGP (derived from X25519 privkey at init)
- Add ROUTER_FLAG_SIGNED (0x08) to SVC_ROUTE_HDR flags byte
- router_send_one_flags: when is_signed, sign [hdr][payload] and append 64-byte sig
- etcp_router_recv_cb: verify Ed25519 signature when ROUTER_FLAG_SIGNED set
- New API: etcp_router_conn_send_signed()
- Drop signed packets if sender node not in routing table or no Ed25519 key
- 5 unit tests in test_etcp_router_unit.c covering OK/tampered/unknown/no-key/short

src/config_parser.h

@@ -103,6 +103,7 @@ struct global_config {
 
     // Debug and logging configuration
     char log_file[256];        // Path to log file (empty = stdout)
+    char db_path[256];         // Path to LMDB nodeinfo database (empty = disabled)
     char debug_level[16];      // debug level: error, warn, info, debug, trace
     int enable_timestamp;      // enable timestamps in logs
     int enable_function_names; // enable function names in logs