Browser pairing, notifications, element hiding; drop the top bar

Pairing decrypts a Chromium browser's cookie store (PBKDF2-HMAC-SHA1
against its Keychain key, then AES-128-CBC) and injects the result into
WKHTTPCookieStore. Only the configured apps' hosts and their sign-in
hosts survive the filter. Browsers are offered most-recently-used first,
since the first entry becomes the default and someone with four
Chromium browsers installed wants the one they actually browse in.

WKWebView defines window.Notification but it does nothing: constructing
one throws no error and shows no banner, so a page believes it notified
you. Measured on the machine as `api=function shim=no` before the shim
was made unconditional; `from page: Odoo - Test notification -> raised`
after.

Anything on a page can be right-clicked away. The rule is re-asserted on
every navigation, because the injected script only carries a snapshot
from when the view was built and a selector added since would otherwise
come back on reload.

The top bar is gone. Navigation lives beside the cog, the nav carries
the traffic lights, and two-finger swipe goes back and forward.

The seed is now the real app list, scoped to exact hosts so a Drive link
inside Gmail switches rather than being swallowed.

src-tauri/gen/schemas/capabilities.json

@@ -1 +1 @@
-{"default":{"identifier":"default","description":"The shell webview. App webviews are deliberately absent: remote content gets no IPC.","local":true,"windows":["main"],"permissions":["core:default","core:window:allow-start-dragging","opener:default"]}}
+{"default":{"identifier":"default","description":"The shell webview. App webviews are deliberately absent: remote content gets no IPC.","local":true,"windows":["main"],"permissions":["core:default","core:window:allow-start-dragging","opener:default","notification:default"]}}