feat: add AI data validation, test data generator, index advisor, and snapshots

Four new killer features leveraging AI (Ollama) and PostgreSQL internals:

- Data Validation: describe quality rules in natural language, AI generates
  SQL to find violations, run with pass/fail results and sample violations
- Test Data Generator: right-click table to generate realistic FK-aware test
  data with AI, preview before inserting in a transaction
- Index Advisor: analyze pg_stat tables + AI recommendations for CREATE/DROP
  INDEX with one-click apply
- Data Snapshots: export selected tables to JSON (FK-ordered), restore from
  file with optional truncate in a transaction

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

src-tauri/src/commands/data.rs

@@ -283,7 +283,7 @@ pub async fn delete_rows(
     Ok(total_affected)
 }
 
-fn bind_json_value<'q>(
+pub(crate) fn bind_json_value<'q>(
     query: sqlx::query::Query<'q, sqlx::Postgres, sqlx::postgres::PgArguments>,
     value: &'q Value,
 ) -> sqlx::query::Query<'q, sqlx::Postgres, sqlx::postgres::PgArguments> {