feat(ui): Online Inbox settings tab + auth-code/PKCE login

New Settings tab: enable toggle, config fields, sign-in/out + status.
OnlineLoginService runs the PKCE loopback flow (Duende.IdentityModel.OidcClient
7.1.0), opens the system browser, captures the callback, hands the refresh
token to the Worker. en/de localized. Fixes: loopback callback URL built from
host:port base (avoids doubled redirect path); PollIntervalSeconds threaded
through the state DTO so it loads instead of resetting to 60.

Visual layout + the live sign-in round-trip need manual verification.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/ClaudeDo.Localization/locales/en.json

@@ -63,6 +63,26 @@
       "daySa": "Sa",
       "daySu": "Su"
     },
+    "onlineInbox": {
+      "tabHeader": "Online Inbox",
+      "enabledLabel": "Enable online inbox sync",
+      "restartHint": "Enabling or disabling takes effect after a Worker restart.",
+      "apiBaseUrlLabel": "API base URL",
+      "apiBaseUrlPlaceholder": "https://inbox.claudedo.kuns.dev",
+      "authorityLabel": "Zitadel authority (issuer URL)",
+      "authorityPlaceholder": "https://auth.example.com",
+      "clientIdLabel": "Client ID",
+      "scopesLabel": "Scopes",
+      "redirectUriLabel": "Redirect URI",
+      "pollIntervalLabel": "Poll interval (seconds)",
+      "statusSection": "AUTH STATUS",
+      "signedInStatus": "Signed in",
+      "signedOutStatus": "Not signed in",
+      "signInButton": "Sign in via browser",
+      "signOutButton": "Sign out",
+      "configSection": "CONFIGURATION",
+      "saveButton": "Save config"
+    },
     "inherit": {
       "inheritedFromList": "inherited · List",
       "inheritedFromGlobal": "inherited · Global",
@@ -427,6 +447,7 @@
     "merge": { "commitMessage": "Merge task: {0}", "workerOfflineBranches": "Worker offline — cannot list branches.", "loadBranchesFailed": "Failed to load branches: {0}", "merged": "Merged.", "conflict": "Merge conflict — target branch restored. Resolve manually or via Continue, then retry.", "blocked": "Blocked: {0}", "unknownStatus": "Unknown status: {0}", "mergeFailed": "Merge failed: {0}" },
     "conflictResolution": { "vsCodeError": "Could not launch VS Code: {0}. Paths are listed above — copy them manually.", "subtaskPrefix": "Conflicts in subtask: {0}", "targetPrefix": "Merging into: {0}" },
     "settingsModal": { "workerOffline": "Worker offline — settings read-only.", "saveFailed": "Save failed: {0}" },
+    "onlineInbox": { "workerOffline": "Worker offline — cannot load config.", "saved": "Config saved.", "saveFailed": "Save failed: {0}", "signedIn": "Signed in successfully.", "signInFailed": "Sign-in failed: {0}", "signedOut": "Signed out.", "signOutFailed": "Sign-out failed: {0}" },
     "weeklyReport": { "invalidRange": "Invalid date range.", "generating": "Generating report…", "error": "Error: {0}" },
     "filesTab": { "workerOffline": "Worker offline.", "noneBundled": "No default agents bundled.", "allPresent": "All default agents already present.", "restored": "Restored {0} default agent(s).", "restoreFailed": "Restore failed: {0}", "openFailed": "Open failed: {0}" },
     "worktreesTab": { "workerOffline": "Worker offline.", "removed": "Removed {0} worktree(s).", "blocked": "Cannot force-remove: {0} task(s) still running. Cancel them first.", "removedFrom": "Removed {0} worktree(s) from {1} task(s)." },