feat: fallback to ctid for editing tables without primary key

When a table has no PRIMARY KEY, use PostgreSQL's ctid (physical row ID)
to identify rows for UPDATE/DELETE operations instead of blocking edits.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src-tauri/src/models/query_result.rs

@@ -20,4 +20,5 @@ pub struct PaginatedQueryResult {
     pub total_rows: i64,
     pub page: u32,
     pub page_size: u32,
+    pub ctids: Vec<String>,
 }