Fix database UI query issues

[DhruvShah-Dev]

Summary

• Use the live selected database list in the object palette and align its multi-database branch with the sidebar.
• Make query error text selectable and add an explicit copy action.
• Render MySQL/MariaDB JSON update values as JSON text instead of CAST(... AS JSON), which MariaDB rejects.

Closes #591.
Closes #608.
Closes #610.

Validation

• pnpm.cmd vitest run tests/components/modals/ErrorModal.test.tsx tests/utils/quickNavigator.test.ts
• pnpm.cmd typecheck
• pnpm.cmd lint
• pnpm.cmd build
• git diff --check
• cargo test mysql_json_update_value --manifest-path src-tauri/Cargo.toml --lib --no-run
• GitHub CI test job passed

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (5 files)

• src-tauri/src/drivers/mysql/mod.rs
• src-tauri/src/drivers/mysql/tests.rs
• src/components/modals/ErrorModal.tsx
• src/components/modals/QuickNavigatorModal.tsx
• tests/components/modals/ErrorModal.test.tsx

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_{Reviewed by step-3.7-flash · Input: 84.7K · Output: 23.1K · Cached: 2.2M}