fix(deploy): writable pretrained dir + safe mkdir fallback

pretrained_registry imported at module load time tried to mkdir
/app/pretrained, which the app user can't write to. Two fixes:
1. Dockerfile now creates /app/pretrained and chowns it to app:app.
2. Module-level mkdir is wrapped in try/except so import never crashes;
warning logged instead. PRETRAINED_DIR overridable via env for hosts
with a read-only app dir (point at /tmp/pretrained on Render free).

Fixes: 'Analiz hatasi: [Errno 13] Permission denied: /app/pretrained'
on every /inspect call.

services/backend/Dockerfile

@@ -78,7 +78,8 @@ COPY --chown=app:app parts.yaml             ./
 
 COPY --chown=app:app scripts/entrypoint.sh /usr/local/bin/entrypoint.sh
 RUN chmod +x /usr/local/bin/entrypoint.sh && \
-    mkdir -p ${MODEL_DIR} && chown -R app:app ${MODEL_DIR}
+    mkdir -p ${MODEL_DIR} /app/pretrained && \
+    chown -R app:app ${MODEL_DIR} /app/pretrained
 
 USER app
 

services/backend/pretrained_registry.py

@@ -38,8 +38,20 @@ from typing import Any, Dict, List, Optional
 # Paths
 # ---------------------------------------------------------------------------
 ML_ROOT = Path(__file__).resolve().parent
-PRETRAINED_DIR = ML_ROOT / "pretrained"
-PRETRAINED_DIR.mkdir(parents=True, exist_ok=True)
+# PRETRAINED_DIR is overridable via env (PRETRAINED_DIR) so production hosts
+# with a read-only application dir can point it at writable scratch space
+# (e.g. /tmp/pretrained on Render, /data on Fly.io).
+PRETRAINED_DIR = Path(os.getenv("PRETRAINED_DIR", str(ML_ROOT / "pretrained")))
+try:
+    PRETRAINED_DIR.mkdir(parents=True, exist_ok=True)
+except (PermissionError, OSError) as _e:
+    import logging as _logging
+    _logging.warning(
+        "pretrained_registry: cannot create %s (%s). Set PRETRAINED_DIR env to "
+        "a writable path or rebuild image with chown on this directory. "
+        "Pretrained model downloads will fail until then.",
+        PRETRAINED_DIR, _e,
+    )
 
 
 # ---------------------------------------------------------------------------