perf: prevent import hanging with timeouts and batching

- verifyAndFixInteractionModesCount: paginated DB queries (500/batch)
  instead of loading all items into memory at once
- withFurniDataLock: add 60s chain timeout to prevent deadlocks
  when a lock holder stalls or crashes
- withGamedataLock: same timeout protection for gamedata locks
- conversion-pool: add 60s per-job timeout, fall back to main thread
- furni/batch: abort signal + post_import progress events + skip
  post-import steps when client disconnects
- furni/batch-regen: abort signal + early exit when disconnected
- clone/sync-all: pre-fetch furnidata once per source instead of
  per item (eliminates 2000+ redundant fetches)
- sse-client: add 60s idle timeout to prevent infinite hangs

src/lib/services/swf/conversion-pool.ts

@@ -87,6 +87,8 @@ function pump() {
 	}
 }
 
+const CONVERSION_TIMEOUT_MS = 60_000;
+
 function run(req: Omit<WorkerRequest, "id">): Promise<WorkerResponse> {
 	if (!ensurePool()) {
 		try {
@@ -118,6 +120,33 @@ function run(req: Omit<WorkerRequest, "id">): Promise<WorkerResponse> {
 		};
 		queue.push(job);
 		pump();
+
+		// Timeout: if a job takes too long, remove it from the queue
+		// and reject so the caller can fall back to main-thread conversion.
+		const timer = setTimeout(() => {
+			const idx = queue.findIndex((j) => j.req.id === job.req.id);
+			if (idx !== -1) {
+				queue.splice(idx, 1);
+				pending.delete(job.req.id);
+				reject(new Error("Conversion timed out"));
+			} else {
+				// Already dispatched to a worker — the worker is
+				// responsible for timing out its own task.
+				reject(new Error("Conversion timed out"));
+			}
+		}, CONVERSION_TIMEOUT_MS);
+
+		// Clear the timer once the job resolves/rejects
+		const origResolve = resolve;
+		const origReject = reject;
+		job.resolve = (r) => {
+			clearTimeout(timer);
+			origResolve(r);
+		};
+		job.reject = (e) => {
+			clearTimeout(timer);
+			origReject(e);
+		};
 	});
 }