fix: identity detail 502 - IdentityDetailRecord.id i32->i64 type mismatch panic

- identities.id is BIGINT (8 bytes), Rust struct was i32 (4 bytes)
- sqlx type mismatch caused panic, crashing backend process
- Proxy returned 502 due to empty reply from crashed backend
- Phase 5: 17/23 passed (was 16/23)

src/core/db/postgres_db.rs

@@ -71,7 +71,7 @@ pub struct FileIdentityRecord {
 
 #[derive(Debug, Clone, Serialize, Deserialize, sqlx::FromRow)]
 pub struct IdentityDetailRecord {
-    pub id: i32,
+    pub id: i64,
     pub uuid: String,
     pub name: String,
     pub identity_type: Option<String>,