feat(ios): add full-text search in data browser

[datlechin]

Summary

• Add server-side full-text search across all columns in the iOS data browser
• Generates CAST(col AS CHAR/TEXT) LIKE '%term%' per column with dialect-aware escaping (MySQL CHAR, PostgreSQL TEXT, SQLite bare column)
• Search ANDs with existing column filters: WHERE (search clauses) AND (filter clauses)
• Integrates with pagination — both data and COUNT queries include the search clause
• Uses native .searchable modifier with on-submit trigger (no debounce)
• Hidden for Redis connections (no SQL)
• Shows ContentUnavailableView.search for empty search results

Test plan

• Open a MySQL/PostgreSQL/SQLite table, search for a value — verify results match
• Search for a numeric value — verify CAST finds it in non-text columns
• Search with special characters (%, _, ') — verify escaping works
• Combine search with column filters — verify AND composition
• Paginate through search results — verify correct counts
• Clear search bar — verify full data reloads
• Open a Redis connection — verify search bar is hidden