Restructure the app shell per docs/UI_UX_PLAN.md phase 1:
- Every destination page gets its own AdwHeaderBar via page_frame(), with
page actions packed into it and a busy spinner beside the title.
- The sidebar is regrouped (files, then a Sync section) with a primary menu
(Preferences, Keyboard Shortcuts, About) and a footer showing sync state,
storage quota and the account with Sign Out.
- The Settings page is gone: startup, folder location, appearance and cache
options move into an AdwPreferencesDialog (Ctrl+,); transfers move to the
Sync page; developer details move into About's debug info.
- Inline CSS moves to a gresource stylesheet using libadwaita colour
variables. The system accent is the default; the Proton purple accent is
an opt-in preference (new `proton_accent` config key, defaults off).
- Add a keyboard shortcuts dialog (Ctrl+?).
libadwaita requirement stays at 1.5, so Ubuntu 24.04 remains supported.
- A queued rename that also changes folder now lands as one `move-multiple`
request carrying the target name instead of rename-then-move, so there is
no half-applied state and no second call for stale name requirements to
hit (B46 follow-up). A destination name collision moves under a conflict
name in one step; same-folder renames still use the rename endpoint.
- Shared with me shows the inviter and invite date (GUI subtitle, `pdfs
shared-with-me`), with a warning when the invitation signature does not
verify against the claimed inviter's keys. `DirEntry` gains `shared_by`,
`shared_at` and `shared_by_unverified`, all serde-defaulted.
- Bump `proton-sdk` / `proton-drive-rs` to 0.6.3 (anonymous-node moves,
`TrashTime` trashed detection).
nvrl
emptyname