feat(mcp): Settings page, per-connection access and activity log #1136

Settings → MCP

• Toggle "Enable MCP server" (off by default). Status: running / port / connected clients.
• Per-connection access: Off (default) / Read. Connections with environment production show a warning; access stays opt-in.
• "Copy config" buttons for Claude Desktop, Cursor, VS Code and a generic stdio snippet, with the absolute path of the bundled querya-mcp.
• "Regenerate token" disconnects current clients.

Activity log

• Last 200 calls: time, client name (from initialize), tool, connection, SQL (truncated), rows, duration, error.
• Stored in LocalDb; also written to the mutation audit with MutationAuditSource.mcp.

UI kit

Build with existing components (QueryaActionButton, QueryaBadge, QueryaEmptyState, QueryaDropdown).

Tests

Widget tests for the toggle, per-connection access, copy-config content (no secrets) and the log list.

Part of #1133.