fix: default logs off, suppress webview context menu, sort queue rows, defer keychain access to user action

- Disable log capture by default in both backend (LOG_PAUSED=true) and
  frontend (isPaused=true) to avoid unnecessary disk I/O and battery drain.
- Add a global contextmenu listener that prevents the webview's default
  right-click menu (Reload, etc.) so the app behaves like a native macOS
  window. Custom context menus in DownloadItem, LogsView, and Sidebar
  still work because their handlers preventDefault() before the document
  listener fires.
- Sort the download table by queuePosition when viewing a specific queue
  so the move-up/down controls produce a visible reorder instead of a
  silent position swap with no UI feedback.
- Rework the keychain access flow to eliminate the OS credential prompt
  that appeared before the app's own KeychainPermissionModal after every
  binary update. hydrate_extension_pairing_token now always skips the
  keychain; only the explicit Grant Access button (grant_keychain_access)
  triggers the OS prompt, which is user-initiated and therefore acceptable
  even when macOS trust resets after a code-signature change.

src-tauri/src/db.rs

@@ -553,6 +553,7 @@ pub fn load_settings(connection: &Connection) -> Result<Option<String>, String>
         .map_err(|error| format!("failed to load settings: {error}"))
 }
 
+#[allow(dead_code)]
 pub fn is_keychain_access_granted(connection: &Connection) -> Result<bool, String> {
     let Some(settings) = load_settings(connection)? else {
         return Ok(false);