feat: v0.4.0 - provider icon system, settings modal & polish

- Add provider icon system with extracted icon library (cc-switch based)

- Persist icon and icon_color in SQLite and config.toml

- Add Settings modal (theme / language / update check / silent download)

- Add useTheme and useUpdateCheck hooks

- Add provider icon picker (IconPicker) with search and grid

- Fix icon frame 2-layer color difference in ProviderEdit

- Dashboard heatmap and daily usage improvements

- Sessions page polish and adaptive layout

- Bump version to 0.4.0

src/i18n/en.ts

@@ -74,6 +74,13 @@ export const enTranslations: Record<TranslationKey, string> = {
   readOnlyPreview: "Editable JSON",
   apply: "Apply",
   invalidJson: "Invalid JSON: {message}",
+  clickToSelectIcon: "Click to select icon",
+  clickToChangeIcon: "Click to change icon",
+  selectIcon: "Select icon",
+  clearIcon: "Clear icon",
+  iconPickerSearch: "Search icons",
+  iconPickerSearchPlaceholder: "Type an icon name...",
+  iconPickerNoResults: "No matching icons found",
 
   // Agent / target
   target: "Target",
@@ -203,6 +210,30 @@ export const enTranslations: Record<TranslationKey, string> = {
   zh: "中文",
   en: "English",
 
+  // Theme & Settings
+  themeLight: "Light",
+  themeDark: "Dark",
+  themeAuto: "Auto",
+  settings: "Settings",
+  settingsTitle: "Settings",
+  settingsAppearance: "Appearance",
+  settingsUpdates: "Updates",
+  settingsAbout: "About",
+  checkUpdate: "Check for updates",
+  checking: "Checking…",
+  upToDate: "You're up to date",
+  updateAvailable: "Update available",
+  currentVersion: "Current version",
+  latestVersion: "Latest version",
+  downloadUpdate: "Download update",
+  downloading: "Downloading…",
+  downloadComplete: "Download complete, click to install",
+  install: "Install",
+  updateCheckFailed: "Update check failed",
+  lastChecked: "Last checked",
+  appDescription: "Windows desktop LLM provider config manager",
+  referenceProject: "Reference project",
+
   // Validation errors
   emptyProviderName: "Provider name is empty",
   duplicateProviderName: "Duplicate provider name: {0}",