feat(i18n): localize installer with language picker and config write-through

- Init Localizer at app startup (before self-update prompt) and assign to TrExtension.Localizer
- Register ILocalizer in DI; inject into WizardViewModel and SettingsViewModel
- WizardViewModel: SelectedLanguage ComboBox binding with OnSelectedLanguageChanged -> SetLanguage + InstallContext.Language
- WizardWindow.xaml: DockPanel wraps step chips + language ComboBox (right-aligned)
- Localize all installer XAML: WizardWindow, WelcomePage, PathsPage, ServicePage, UiSettingsPage, InstallPage, SettingsWindow, SelfUpdatePromptWindow
- Localize page Title properties and WizardViewModel.NextButtonText via TrExtension.Localizer
- Persist chosen Language in WriteConfigStep and SettingsViewModel.Save into ui.config.json
- Append installer section to en.json (nav, welcome, paths, service, uiSettings, install, settings, selfUpdate)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/ClaudeDo.Localization/locales/en.json

@@ -262,6 +262,67 @@
       "emptyStateHint": "No report for this range yet. Click “Generate”."
     }
   },
+  "installer": {
+    "nav": {
+      "back": "Back",
+      "next": "Next →",
+      "install": "Install",
+      "browse": "Browse...",
+      "cancel": "Cancel"
+    },
+    "welcome": {
+      "title": "Welcome",
+      "heading": "Install ClaudeDo",
+      "subheading": "Choose where to install ClaudeDo, then click Next.",
+      "updateSubheading": "Your tasks, config, and database will be preserved. Click Next to continue.",
+      "installDirectory": "Install Directory",
+      "registerMcp": "Register MCP server with Claude",
+      "registerMcpHint": "Runs 'claude mcp add' so Claude can view and manage your ClaudeDo tasks. You can change this later."
+    },
+    "paths": {
+      "title": "Data Paths",
+      "subtitle": "Configure where ClaudeDo stores its data.",
+      "databasePath": "Database Path",
+      "logDirectory": "Log Directory",
+      "sandboxRoot": "Sandbox Root",
+      "worktreeStrategy": "Worktree Strategy",
+      "centralWorktreeRoot": "Central Worktree Root"
+    },
+    "service": {
+      "title": "Worker",
+      "subtitle": "Configure the ClaudeDo background worker.",
+      "signalRPort": "SignalR Port",
+      "queueBackstopInterval": "Queue Backstop Interval (ms)",
+      "claudeCliPath": "Claude CLI Path",
+      "autostart": "Start worker automatically at logon",
+      "autostartHint": "The worker runs as you (the logged-in user) via a per-user logon task, so it can use your Claude CLI authentication.",
+      "restartDelay": "Restart Delay (ms)"
+    },
+    "uiSettings": {
+      "title": "UI Settings",
+      "subtitle": "Configure the ClaudeDo desktop UI connection settings.",
+      "syncWithService": "Sync with service settings",
+      "signalRUrl": "SignalR URL",
+      "syncHint": "When synced, these values are derived from the Service and Paths pages."
+    },
+    "install": {
+      "title": "Installation",
+      "subtitle": "Click Install to build and deploy ClaudeDo.",
+      "launch": "Launch ClaudeDo"
+    },
+    "settings": {
+      "removeUserData": "Remove user data (tasks, logs, configs in ~/.todo-app)",
+      "uninstall": "Uninstall",
+      "repair": "Repair",
+      "save": "Save",
+      "close": "Close"
+    },
+    "selfUpdate": {
+      "heading": "A newer installer is available",
+      "update": "Update",
+      "continueAnyway": "Continue anyway"
+    }
+  },
   "planning": {
     "conflict": {
       "windowTitle": "Merge conflict",