feat(linux): open SQLite files with Cellar

Goal

Bring the SQLite file-opening workflow to Linux GPUI packages after Linux distribution support is added.

Users should be able to:

• open .db, .db3, .sdb, .sqlite, and .sqlite3 files with Cellar from a file manager;
• choose Cellar from Open With;
• drag a SQLite file into the Cellar 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 Linux desktop integration (.desktop MimeType/Exec entries and shared-mime-info where needed), plus launch or single-instance forwarding so file paths reach the running app. Verify both Wayland and X11 drag/drop behavior.

Acceptance criteria

• Linux packages advertise Cellar for the supported SQLite extensions/MIME types.
• 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.
• Drag/drop is verified under both Wayland and X11.
• Paths containing spaces and non-ASCII characters work.
• Packaging updates refresh the required desktop and MIME databases.
• Packaged-build/manual verification steps are documented or automated.