refactor: Modularize Electron main process into single-responsibility components

Extract the monolithic main.ts (~1000 lines) into focused modules:

- electron/constants.ts - Window sizing, port defaults, filenames
- electron/state.ts - Shared state container
- electron/utils/ - Port availability and icon utilities
- electron/security/ - API key management
- electron/windows/ - Window bounds and main window creation
- electron/server/ - Backend and static server management
- electron/ipc/ - IPC handlers with shared channel constants

Benefits:
- Improved testability with isolated modules
- Better discoverability and maintainability
- Single source of truth for IPC channels (used by both main and preload)
- Clear separation of concerns

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/ui/src/electron/utils/icon-manager.ts

@@ -0,0 +1,45 @@
+/**
+ * Icon management utilities
+ *
+ * Functions for getting the application icon path.
+ */
+
+import path from 'path';
+import { app } from 'electron';
+import { electronAppExists } from '@automaker/platform';
+import { createLogger } from '@automaker/utils/logger';
+
+const logger = createLogger('IconManager');
+
+/**
+ * Get icon path - works in both dev and production, cross-platform
+ * Uses centralized electronApp methods for path validation.
+ */
+export function getIconPath(): string | null {
+  const isDev = !app.isPackaged;
+
+  let iconFile: string;
+  if (process.platform === 'win32') {
+    iconFile = 'icon.ico';
+  } else if (process.platform === 'darwin') {
+    iconFile = 'logo_larger.png';
+  } else {
+    iconFile = 'logo_larger.png';
+  }
+
+  const iconPath = isDev
+    ? path.join(__dirname, '../../public', iconFile)
+    : path.join(__dirname, '../../dist/public', iconFile);
+
+  try {
+    if (!electronAppExists(iconPath)) {
+      logger.warn('Icon not found at:', iconPath);
+      return null;
+    }
+  } catch (error) {
+    logger.warn('Icon check failed:', iconPath, error);
+    return null;
+  }
+
+  return iconPath;
+}