Merge PR #151 from aakhter/cod-167-heic-jpeg-conversion: convert HEIC paste uploads to JPEG

Includes review fixes: worker-thread conversion with resourceLimits + timeout, global conversion-limiter cap, 64MP pre-decode bomb guard, magic-byte detection (covers mislabeled Android HEIF).

src/types/heic-decode.d.ts

@@ -0,0 +1,24 @@
+declare module 'heic-decode' {
+  export interface DecodedHeicImage {
+    width: number;
+    height: number;
+    data: Uint8ClampedArray;
+  }
+
+  /** Handle exposing header-declared dimensions WITHOUT decoding pixels. */
+  export interface HeicImageHandle {
+    width: number;
+    height: number;
+    decode(): Promise<DecodedHeicImage>;
+  }
+
+  export type HeicImageHandles = HeicImageHandle[] & { dispose(): void };
+
+  interface HeicDecode {
+    (input: { buffer: Buffer | Uint8Array }): Promise<DecodedHeicImage>;
+    all(input: { buffer: Buffer | Uint8Array }): Promise<HeicImageHandles>;
+  }
+
+  const decode: HeicDecode;
+  export default decode;
+}