feat(w5): ship v2.0.0 platform sync, undo persistence, and updates

Co-authored-by: Cursor <cursoragent@cursor.com>

public/locales/en/translation.json

@@ -589,5 +589,50 @@
   "readMode.fontSerif": "Serif",
   "readMode.fontSans": "Sans-serif",
   "readMode.fontEyeCare": "Eye care",
-  "readMode.tts": "Read aloud"
+  "readMode.tts": "Read aloud",
+  "settings.extensions": "Extensions",
+  "sync.title": "Cloud sync",
+  "sync.desc": "Sync encrypted backup of all books to WebDAV or a local folder",
+  "sync.mode": "Sync mode",
+  "sync.modeLocal": "Local folder",
+  "sync.modeWebdav": "WebDAV",
+  "sync.localPathPlaceholder": "Sync folder path",
+  "sync.pickFolder": "Pick folder",
+  "sync.webdavUrl": "WebDAV URL",
+  "sync.webdavUser": "WebDAV username",
+  "sync.schedule": "Schedule",
+  "sync.scheduleManual": "Manual",
+  "sync.scheduleHourly": "Hourly",
+  "sync.scheduleDaily": "Daily",
+  "sync.scheduleWeekly": "Weekly",
+  "sync.passwordPlaceholder": "Sync password (min 8 chars)",
+  "sync.passwordHint": "Set a sync password with at least 8 characters",
+  "sync.saveConfig": "Save sync config",
+  "sync.runNow": "Sync now",
+  "sync.running": "Syncing…",
+  "sync.done": "Sync complete",
+  "sync.configSaved": "Sync config saved",
+  "sync.lastSync": "Last sync: {{time}} ({{status}})",
+  "sync.conflictTitle": "Sync conflict",
+  "sync.conflictDesc": "Both local and remote changed. Choose which copy to keep.",
+  "sync.useRemote": "Use remote",
+  "sync.useLocal": "Use local",
+  "extensions.title": "Extensions",
+  "extensions.desc": "Extension API skeleton (no third-party code execution)",
+  "extensions.devMode": "Developer mode (manifest validation only)",
+  "extensions.stubHint": "Full extension marketplace coming in a future release.",
+  "update.available": "Update {{version}} available",
+  "update.download": "Download update",
+  "update.downloading": "Downloading {{percent}}%",
+  "update.install": "Restart to install",
+  "crash.title": "Unclean shutdown detected",
+  "crash.desc": "The app may have exited unexpectedly last time. You can send a local log report (stub).",
+  "crash.send": "Send report",
+  "crash.dismiss": "Dismiss",
+  "ai.settings.builtinSkills": "Built-in skills",
+  "ai.settings.skillContinue": "Continue writing",
+  "ai.settings.skillPolish": "Polish",
+  "ai.settings.skillProofread": "Proofread",
+  "ai.settings.mcpConnector": "MCP connector URL",
+  "ai.settings.mcpTest": "Test connection"
 }