feat: multi-run support — execute N times with one click

- Side Panel: number input next to Auto button (1-50)
- Background: autoRunLoop wraps full flow in a for-loop
  - Each run: reset state (keep VPS/mail settings) → steps 1-9
  - Pause for email on each run, resume continues
  - Stop on error
- Side Panel shows run progress: "Running (2/5)", "Paused (3/5)"
- AUTO_RUN_RESET message resets UI between runs
- Default mail provider changed to 163
- 163 mail: faster polling (500ms intervals), skip child iframe ready signals

content/utils.js

@@ -224,4 +224,8 @@ function sleep(ms) {
 }
 
 // Auto-report ready on load
-reportReady();
+// Skip ready signal from child iframes of mail pages to avoid overwriting the top frame's registration
+const _isMailChildFrame = (SCRIPT_SOURCE === 'qq-mail' || SCRIPT_SOURCE === 'mail-163') && window !== window.top;
+if (!_isMailChildFrame) {
+  reportReady();
+}