efactor(extension): modularize dashboard, background, and docs

Split monolithic dashboard.js (2753 lines) into 18 focused modules
under dashboard/{core,data,ui,pages}/ with refresh.js and events.js
as orchestrators. Extracted ~900-line inline <style> into dashboard.css
and moved dashboard.html to dashboard/dashboard.html.

Split background.js (609 lines) into background/{logs,state,proxy,
native-messaging,tab-lifecycle,message-router}.js with a thin entry
point using importScripts().

Deleted dead files: wrong-domain.js (duplicate of inline script).
Updated manifest.json web_accessible_resources for new paths.
Updated docs/ARCHITECTURE.md to reflect the new file structure.

No functionality changed. No build step introduced.

extension/dashboard/events.js

@@ -0,0 +1,30 @@
+// Global event wiring — toggle switches, settings buttons, and per-page setup calls.
+// Depends on: all page modules
+
+function setupEvents() {
+  // Toggle switches
+  document.querySelectorAll('.toggle').forEach(toggle => {
+    toggle.addEventListener('click', () => toggle.classList.toggle('active'));
+  });
+
+  // Save settings
+  $('btnSaveSettings')?.addEventListener('click', saveSettings);
+
+  // Reset settings to defaults
+  $('btnResetSettings')?.addEventListener('click', () => {
+    settings = { ...SETTINGS_DEFAULTS };
+    chrome.runtime.sendMessage(
+      { target: 'holesail-native', action: 'send', payload: { type: 'updateSettings', payload: { ...settings } } },
+      (response) => {
+        if (response && response.settings) settings = { ...SETTINGS_DEFAULTS, ...response.settings };
+        updateSettingsUI();
+        showToast('Settings reset to defaults', 'success');
+      }
+    );
+  });
+
+  setupVirtualHostEvents();
+  setupServerEvents();
+  setupServiceTunnelEvents();
+  setupLogsEvents();
+}