feat: persistent query history for iOS

[datlechin]

Summary

• Query history persists to disk (JSON in Application Support)
• Shows timestamps (relative date), scoped per connection
• Swipe-to-delete individual entries, Clear All button
• Max 200 entries with FIFO eviction, deduplicates consecutive queries
• Native Form sheet with .insetGrouped list

Test plan

• Run queries — appear in history with timestamps
• Close and reopen app — history persists
• Tap history entry — inserts into editor
• Swipe to delete — removed from disk
• Clear All — wipes history for current connection
• Switch connections — each has its own history