Drop cookie import; click-through notifications; per-app zoom

The cookie import is gone. It worked mechanically - 43 cookies decrypted
from Arc and verifiably visible to the page - but Google, Microsoft and
Odoo all refused the imported sessions, because each binds a session to
the browser that created it. Signing in once inside the app is simpler
and actually works, so the whole path is deleted rather than kept as a
feature that mostly fails. That takes rusqlite, aes, cbc, pbkdf2, hmac,
sha1 and sha2 out of the build with it.

Notifications are now raised through mac-notification-sys rather than
Tauri's notification plugin, because the plugin cannot report that one
was clicked. A click switches to the app that raised it and then runs
the page's own click handler - the only thing that knows which message
the notification was about.

Zoom is per app, on a fixed ladder so Cmd+0 returns to exactly 100%.
The shortcuts are menu-bar accelerators rather than a key listener,
since the keystroke has to work while a remote page has focus.

The hidden-element count is off the nav rows.

src-tauri/src/config.rs

@@ -33,10 +33,18 @@ pub struct App {
     /// the thing you never want to see again.
     #[serde(default)]
     pub hidden: Vec<String>,
+    /// Page zoom, remembered per app: a dense ERP and a mail client do not
+    /// want the same size.
+    #[serde(default = "default_zoom")]
+    pub zoom: f64,
     #[serde(default)]
     pub order: i32,
 }
 
+fn default_zoom() -> f64 {
+    1.0
+}
+
 impl App {
     pub fn scopes(&self) -> Vec<String> {
         if self.scope.is_empty() {
@@ -69,10 +77,6 @@ pub struct Settings {
     pub nav_collapsed: bool,
     #[serde(default = "default_theme")]
     pub theme: String,
-    #[serde(default)]
-    pub paired_browser: Option<String>,
-    #[serde(default)]
-    pub last_paired_at: Option<String>,
 }
 
 fn default_theme() -> String {
@@ -84,8 +88,6 @@ impl Default for Settings {
         Self {
             nav_collapsed: false,
             theme: default_theme(),
-            paired_browser: None,
-            last_paired_at: None,
         }
     }
 }
@@ -185,6 +187,7 @@ pub fn seed() -> Config {
         group_id: Some(group.into()),
         user_agent: None,
         hidden: Vec::new(),
+        zoom: 1.0,
         order,
     };
     Config {
@@ -291,6 +294,8 @@ mod tests {
         assert_eq!(cfg.version, 1);
         assert_eq!(cfg.settings.theme, "system");
         assert_eq!(cfg.apps[0].scopes(), vec!["x.com".to_string()]);
+        // A file written before zoom existed must not open every app at 0%.
+        assert_eq!(cfg.apps[0].zoom, 1.0);
         assert!(cfg.apps[0].ua().contains("Chrome/"));
     }
 }