feat: identity PATCH update, alias system, name UNIQUE removal

- Add PATCH /api/v1/identity/:identity_uuid endpoint
- Migration 030: remove name UNIQUE, add tmdb_id index
- TMDb upsert: ON CONFLICT (name) -> ON CONFLICT (tmdb_id)
- get_or_create_identity: pre-check by name
- upload_identity: ON CONFLICT (name) -> ON CONFLICT (uuid)
- Search: include aliases in identity text search
- Add scripts/llm_metadata_enhancer.py
- Add DESIGN/IdentityUpdateAndAliasSystem.md

src/core/db/postgres_db.rs

@@ -3210,12 +3210,27 @@ impl PostgresDb {
 
     pub async fn get_or_create_identity(&self, name: &str) -> Result<i32> {
         let identities_table = schema::table_name("identities");
-        let id: i32 = sqlx::query_scalar(&format!(
-            "INSERT INTO {} (name, identity_type, source, status) VALUES ($1, 'people', 'user_defined', 'confirmed') \
-             ON CONFLICT (name) DO UPDATE SET updated_at = CURRENT_TIMESTAMP RETURNING id", identities_table
+        // First: try to find existing identity by name
+        if let Some(id) = sqlx::query_scalar::<_, i32>(&format!(
+            "SELECT id FROM {} WHERE name = $1 LIMIT 1",
+            identities_table
         ))
         .bind(name)
-        .fetch_one(&self.pool).await?;
+        .fetch_optional(&self.pool)
+        .await?
+        {
+            return Ok(id);
+        }
+        // Not found: create new with generated uuid
+        let id: i32 = sqlx::query_scalar(&format!(
+            "INSERT INTO {} (uuid, name, identity_type, source, status) \
+             VALUES (gen_random_uuid(), $1, 'people', 'user_defined', 'confirmed') \
+             RETURNING id",
+            identities_table
+        ))
+        .bind(name)
+        .fetch_one(&self.pool)
+        .await?;
         Ok(id)
     }
 }