feat(peer): coordinate outbound transfers with local game mutations

Updating or removing a local game rewrites its on-disk files. Peers that
were mid-download of that game would keep streaming bytes from files that
are being deleted or replaced, handing them a corrupt or stale copy.
There was also no authoritative notion of which game version a peer
should serve or accept, so a peer could serve whatever happened to be on
disk and downloaders could aggregate files from peers running mismatched
versions.

This introduces a reader-writer coordination scheme between outbound file
transfers (readers) and local mutation operations (writers), and gates
both serving and downloading on an authoritative game catalog version.

Reader-writer coordination:
- Track active outbound transfers per game in a shared `OutboundTransfers`
  map of (id, CancellationToken), threaded through `Ctx`/`PeerCtx` and
  registered by a `TransferGuard` in the stream service. The guard is
  registered *before* the serve-eligibility check to close a TOCTOU window
  where a writer could miss an in-flight reader.
- `stream_file_bytes` now honors a cancellation token at every await point
  (file read, network send, stream close) via `tokio::select!`, so a
  transfer aborts promptly instead of hanging on a stalled receiver.
- `begin_operation` marks a game active first, then cancels its outbound
  transfers and waits for the count to reach zero before any
  Updating/RemovingDownload work touches the filesystem.
- Active games are now hidden from library snapshots entirely while an
  operation is in flight, instead of freezing their last announced state,
  so peers stop discovering a game that is being mutated.

Authoritative version catalog:
- Replace the `HashSet<String>` catalog with `GameCatalog`, mapping each
  game id to its expected version (from the bundled game.db / ETI data).
- Serving requires the local `version.ini` to match the catalog version
  (`local_download_matches_catalog`); peer selection, file aggregation,
  and majority size validation all filter on the expected version
  (`peers_with_expected_version`, `aggregated_game_files`, and friends).

User-visible changes:
- The GUI shows confirmation dialogs before Update and Remove, and
  surfaces a sharing-status indicator on game cards and the detail modal.
- A new `OutboundTransferCountChanged` event lets the UI reflect live
  outbound transfer activity.

Test Plan:
- just test
- just frontend-test
- just clippy

crates/lanspread-tauri-deno-ts/src/styles/launcher.css

@@ -739,6 +739,12 @@
 .card-status.is-error {
   color: #f87171;
 }
+.card-status.is-warning {
+  color: #fbbf24;
+}
+.card-status.is-info {
+  color: #60a5fa;
+}
 
 .density-compact .card-body {
   padding: 9px 10px 10px;
@@ -1383,6 +1389,16 @@
   border-color: rgba(239, 68, 68, 0.4);
   background: rgba(239, 68, 68, 0.08);
 }
+.modal-status.is-warning {
+  color: #fbbf24;
+  border-color: rgba(245, 158, 11, 0.4);
+  background: rgba(245, 158, 11, 0.08);
+}
+.modal-status.is-info {
+  color: #60a5fa;
+  border-color: rgba(96, 165, 250, 0.4);
+  background: rgba(96, 165, 250, 0.08);
+}
 .modal-actions {
   display: flex;
   align-items: center;