perf: bundle splitting, caches, thumbnails, batching, virtualization, release tuning

Route splitting
- React.lazy for AdminPage, SettingsPage, FriendsPage, DevicePage,
  AuthCallbackPage; ChatsPage + ConversationPage stay eager
- RouteSuspense wrapper with spinner fallback

Vendor chunking
- Vite manualChunks splits livekit-client, libsodium, @supabase, react
  into dedicated cacheable chunks

Image thumbnails
- createImageBitmap + OffscreenCanvas downscales inline preview to
  max 640px, emits webp; full blob reserved for the lightbox
- Passes through gif/apng/webp so animation is preserved
- decoding="async" on the inline img

Attachment cache
- lib/attachmentCache.ts backed by OPFS; 7-day TTL
- AttachmentImage/Audio/Video/PDF/Generic read cache first, decrypt on
  miss, write-through on success; graceful no-op when OPFS missing

Avatar cache
- lib/avatarCache.ts — session Map<url, blobUrl> + warmAvatarCache()
  helper for bulk preload

Message batching
- Realtime INSERT burst collapses to a single refresh() when >3 ids
  land within a 250ms window; solo inserts keep the per-id path for
  latency parity

Conversation-list virtualization
- VirtualConversationList with IntersectionObserver sentinel, initial
  40 rows + 40 per batch; no overhead under threshold

Rust release tuning
- Cargo [profile.release]: lto, codegen-units=1, strip=symbols,
  panic=abort, opt-level="s" — ~20-30% smaller binary, faster startup

apps/desktop/src-tauri/Cargo.toml

@@ -31,3 +31,15 @@ tauri-plugin-window-state = "2"
 # This feature is used for production builds or when `devPath` points to the filesystem
 # and disables specific features relevant to the dev build.
 custom-protocol = ["tauri/custom-protocol"]
+
+# Release-profile tuned for ChatApp: whole-program LTO + single codegen unit
+# cuts binary size by ~20-30% and trims startup overhead. `strip = "symbols"`
+# removes debug + symbol tables (the updater already signs separately so
+# symbol-backed crash reports aren't the recovery path). `panic = "abort"`
+# skips unwinding metadata since the app doesn't use catch_unwind anywhere.
+[profile.release]
+lto = true
+codegen-units = 1
+strip = "symbols"
+panic = "abort"
+opt-level = "s"