feat(windows): open SQLite files with Cellar

Goal

Bring the SQLite file-opening workflow to the Windows GPUI release after Windows packaging is supported.

Users should be able to:

• double-click .db, .db3, .sdb, .sqlite, and .sqlite3 files associated with Cellar;
• use Open with → Cellar;
• drag a SQLite file onto the Cellar app/window;
• open a file while Cellar is already running without creating a duplicate saved connection.

Implementation notes

Reuse the shared GPUI SQLite path handling introduced for macOS. Add the Windows-specific installer/file-association registration and whichever launch or single-instance forwarding path is required to deliver file paths to the running app. Keep Cellar an optional handler rather than taking over generic .db files without user choice.

Acceptance criteria

• Windows packages register Cellar as an available handler for the supported SQLite extensions.
• Cold-start file opening creates, saves, connects, and expands a local SQLite connection.
• Opening a file in an already-running app focuses/reuses the matching canonical-path connection.
• Finder-equivalent drag/drop behavior is verified in the GPUI window.
• Paths containing spaces and non-ASCII characters work.
• Packaged-build/manual verification steps are documented or automated.