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/components/grid/GameCard.tsx

@@ -3,6 +3,7 @@ import { JSX, KeyboardEvent } from 'react';
 import { Game } from '../../lib/types';
 import { CoverAspect } from '../../hooks/useSettings';
 import { formatBytes } from '../../lib/format';
+import { hasNewerLocalVersion } from '../../lib/gameState';
 
 import { GameCover } from './GameCover';
 import { StateChip } from '../StateChip';
@@ -42,6 +43,14 @@ export const GameCard = ({
             onOpen(game);
         }
     };
+    const newerThanExpected = hasNewerLocalVersion(game);
+    const hasOutbound = game.active_outbound_transfers !== undefined && game.active_outbound_transfers > 0;
+    const statusMessage = hasOutbound
+        ? `Sharing to ${game.active_outbound_transfers} peer${game.active_outbound_transfers === 1 ? '' : 's'}`
+        : (game.status_message ?? (newerThanExpected ? 'Newer than expected' : ''));
+    const statusLevel = hasOutbound
+        ? 'info'
+        : (game.status_level ?? (newerThanExpected ? 'warning' : undefined));
 
     return (
         <button
@@ -66,8 +75,8 @@ export const GameCard = ({
                 <div className="card-meta">
                     {metaSeparator(formatBytes(game.size), game.genre || null)}
                 </div>
-                <div className={`card-status${game.status_level === 'error' ? ' is-error' : ''}`}>
-                    {game.status_message ?? ''}
+                <div className={`card-status${statusLevel ? ` is-${statusLevel}` : ''}`}>
+                    {statusMessage}
                 </div>
                 <ActionButton
                     game={game}