feat: restore-all session recovery, ?file= deep links, offline PWA

Session recovery: more than one pending snapshot adds a 'Restore all'
button to the Recover Drawing modal — every snapshot goes through the
exact same guarded path as a single restore (deleted only after its
own open succeeds). The open-tab list and active tab persist to
localStorage on web (open/save/close) and the remembered tab is
re-selected once a restore batch settles; the modal notes how many
drawings the session had. Nothing is auto-opened.

Deep links: ?file=<url|name> opens a drawing at boot. http(s) URLs
must end in .dwg/.dxf and are fetched with the same streaming,
64 MB-capped, 8 s-deadline reader the remote images use, then go
through the guarded open queue; cross-origin opens announce the
origin first. Bare names resolve from the browser's recent storage,
with a hint when absent. Everything else (file:, javascript:, drive
letters, non-drawing tails) is refused with a console note.

Offline PWA: the app was installable (manifest) but downloaded its
55 MB bundle on every visit. A cache-first service worker now serves
the whole bundle from Cache Storage after one online visit —
navigations network-first so updates land, hashed assets
stale-while-revalidate, non-GET/cross-origin passthrough, old caches
cleaned on activate, and the waiting-worker update flow documented.
The build wrapper stamps the cache version from the bundle hash and
hard-fails if sw.js is missing or unstamped.

Also fixes a locale group mismatch on the DATALINK pick notice
(catalog said a display group that does not exist in the ftl
sources).

Cargo.toml

@@ -164,6 +164,9 @@ web-sys = { version = "=0.3.85", features = [
     "Event",
     "ReadableStreamDefaultReader",
     "ReadableStream",
+    # The ?file= boot deep link reads location.search and compares the link's
+    # origin against the page's (io::web_link).
+    "Location",
 ] }
 iced = { git = "https://github.com/iced-rs/iced.git", rev = "23604ff22ab0aad9e00b9327cb7b8546ed84db39", features = ["webgl", "fira-sans"] }