feat: kill all silent fallbacks — fail clearly, never degrade silently

Remove 9 silent fallback chains in the Python sidecar:
- upscale: RealESRGAN→Lanczos (now errors with install guidance)
- upscale: GFPGAN skip (now errors with install guidance)
- gpu: GPU→CPU (now reports device in response, never silent)
- remove_bg: alpha matting fallback (now errors with retry guidance)
- remove_bg: GPU→CPU session (now reports device)
- colorize: DDColor→OpenCV (now errors with install guidance)
- enhance_faces: CodeFormer→GFPGAN (now errors with install guidance)
- ocr: quality cascade (now errors at requested level)
- bridge: dispatcher crash retry (now reports retry in stderr)

Also: raise red_eye max_faces 10→50, face_landmarks max_num_faces configurable,
restore.py min face size 48→24px.

packages/ai/src/bridge.ts

@@ -390,14 +390,14 @@ export function runPythonWithProgress(
   const dispatcherPromise = dispatcherRun(scriptName, args, options);
   if (dispatcherPromise) {
     return dispatcherPromise.catch((err: Error) => {
-      // Dispatcher crashed mid-request (e.g. OOM when loading a large model).
-      // Retry in an isolated per-request process which starts clean and has
-      // more available memory than the warm dispatcher.
       if (err.message === "Python dispatcher exited unexpectedly") {
         console.warn(
           `[bridge] Dispatcher crashed during ${scriptName}, retrying with per-request process`,
         );
-        return runPythonPerRequest(scriptName, args, options);
+        return runPythonPerRequest(scriptName, args, options).then((result) => ({
+          ...result,
+          stderr: `${result.stderr}\n[bridge] retried after dispatcher crash`,
+        }));
       }
       throw err;
     });