feat(assets): standardize asset configuration with capacitor-assets

- Replace manual ImageMagick scripts with official capacitor-assets toolchain
- Consolidate duplicate asset sources to single resources/ directory
- Implement comprehensive asset configuration schema and validation
- Add CI safeguards for asset validation and platform asset detection
- Convert capacitor.config.json to TypeScript format
- Pin Node.js version for deterministic builds
- Remove legacy manual asset generation scripts:
  * generate-icons.sh, generate-ios-assets.sh, generate-android-icons.sh
  * check-android-resources.sh, check-ios-resources.sh
  * purge-generated-assets.sh
- Add new asset management commands:
  * assets:config - generate/update configurations
  * assets:validate - validate configurations
  * assets:clean - clean generated assets (dev only)
  * build:native - build with asset generation
- Create GitHub Actions workflow for asset validation
- Update documentation with new asset management workflow

This standardization eliminates asset duplication, improves build reliability,
and provides a maintainable asset management system using Capacitor defaults.

Breaking Changes: Manual asset generation scripts removed
Migration: Assets now sourced from resources/ directory only
CI: Automated validation prevents committed platform assets

capacitor.config.ts

@@ -0,0 +1,116 @@
+import { CapacitorConfig } from '@capacitor/cli';
+
+const config: CapacitorConfig = {
+  appId: 'app.timesafari',
+  appName: 'TimeSafari',
+  webDir: 'dist',
+  server: {
+    cleartext: true
+  },
+  plugins: {
+    App: {
+      appUrlOpen: {
+        handlers: [
+          {
+            url: 'timesafari://*',
+            autoVerify: true
+          }
+        ]
+      }
+    },
+    SplashScreen: {
+      launchShowDuration: 3000,
+      launchAutoHide: true,
+      backgroundColor: '#ffffff',
+      androidSplashResourceName: 'splash',
+      androidScaleType: 'CENTER_CROP',
+      showSpinner: false,
+      androidSpinnerStyle: 'large',
+      iosSpinnerStyle: 'small',
+      spinnerColor: '#999999',
+      splashFullScreen: true,
+      splashImmersive: true
+    },
+    CapSQLite: {
+      iosDatabaseLocation: 'Library/CapacitorDatabase',
+      iosIsEncryption: false,
+      iosBiometric: {
+        biometricAuth: false,
+        biometricTitle: 'Biometric login for TimeSafari'
+      },
+      androidIsEncryption: false,
+      androidBiometric: {
+        biometricAuth: false,
+        biometricTitle: 'Biometric login for TimeSafari'
+      },
+      electronIsEncryption: false
+    }
+  },
+  ios: {
+    contentInset: 'never',
+    allowsLinkPreview: true,
+    scrollEnabled: true,
+    limitsNavigationsToAppBoundDomains: true,
+    backgroundColor: '#ffffff',
+    allowNavigation: [
+      '*.timesafari.app',
+      '*.jsdelivr.net',
+      'api.endorser.ch'
+    ]
+  },
+  android: {
+    allowMixedContent: true,
+    captureInput: true,
+    webContentsDebuggingEnabled: false,
+    allowNavigation: [
+      '*.timesafari.app',
+      '*.jsdelivr.net',
+      'api.endorser.ch',
+      '10.0.2.2:3000'
+    ]
+  },
+  electron: {
+    deepLinking: {
+      schemes: ['timesafari']
+    },
+    buildOptions: {
+      appId: 'app.timesafari',
+      productName: 'TimeSafari',
+      directories: {
+        output: 'dist-electron-packages'
+      },
+      files: [
+        'dist/**/*',
+        'electron/**/*'
+      ],
+      mac: {
+        category: 'public.app-category.productivity',
+        target: [
+          {
+            target: 'dmg',
+            arch: ['x64', 'arm64']
+          }
+        ]
+      },
+      win: {
+        target: [
+          {
+            target: 'nsis',
+            arch: ['x64']
+          }
+        ]
+      },
+      linux: {
+        target: [
+          {
+            target: 'AppImage',
+            arch: ['x64']
+          }
+        ],
+        category: 'Utility'
+      }
+    }
+  }
+};
+
+export default config;