fix: prevent RAM spike from large PCM files (e.g. 2h elevator)

- Check file size with statSync BEFORE reading into memory
- Files >50MB (~4.5min PCM) are never loaded into RAM, always streamed
- Also skip if total cache would exceed limit (no more read-then-discard)
- Fixes 1GB+ RAM spike when playing long audio files

server/src/index.ts

@@ -162,19 +162,20 @@ fs.mkdirSync(NORM_CACHE_DIR, { recursive: true });
 // Danach kein Disk-I/O mehr bei Cache-Hits -> nahezu instant playback.
 const pcmMemoryCache = new Map<string, Buffer>();
 const PCM_MEMORY_CACHE_MAX_MB = Number(process.env.PCM_CACHE_MAX_MB ?? '512');
+const PCM_PER_FILE_MAX_MB = 50; // Max 50 MB pro Datei (~4.5 min PCM) - groessere werden gestreamt
 let pcmMemoryCacheBytes = 0;
 
 function getPcmFromMemory(cachedPath: string): Buffer | null {
   const buf = pcmMemoryCache.get(cachedPath);
   if (buf) return buf;
-  // Erste Anfrage: von Disk in RAM laden
   try {
+    // Dateigroesse VORHER pruefen - keine grossen Files in den RAM laden
+    const stat = fs.statSync(cachedPath);
+    if (stat.size > PCM_PER_FILE_MAX_MB * 1024 * 1024) return null;
+    if (pcmMemoryCacheBytes + stat.size > PCM_MEMORY_CACHE_MAX_MB * 1024 * 1024) return null;
     const data = fs.readFileSync(cachedPath);
-    const newTotal = pcmMemoryCacheBytes + data.byteLength;
-    if (newTotal <= PCM_MEMORY_CACHE_MAX_MB * 1024 * 1024) {
     pcmMemoryCache.set(cachedPath, data);
-      pcmMemoryCacheBytes = newTotal;
+    pcmMemoryCacheBytes += data.byteLength;
-    }
     return data;
   } catch { return null; }
 }