fix: INSIGHTFACE_HOME path, entrypoint, caching default, CRON_SCHEDULE opt-in

- Dockerfile: ENV INSIGHTFACE_HOME=/models → /models/.insightface to
  match compose.yml and .env.example; the old value caused InsightFace
  to store models at /models/models/buffalo_l (double-appended subdir)
- entrypoint.sh: use /app/.venv/bin/winnow (installed entry point)
  instead of python -m winnow.cli
- config.py: ENABLE_CACHE default false → true; embedding cache is
  always beneficial in practice; users can opt out with ENABLE_CACHE=false
- compose.yml: comment out CRON_SCHEDULE so scheduling is opt-in;
  flip ENABLE_CACHE to commented opt-out to reflect new default
- README.md: update ENABLE_CACHE default documentation to true
- tests/test_config.py: update default assertion to match

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

winnow/config.py

@@ -39,8 +39,7 @@ class _Config:
     USE_FULL_RESOLUTION: bool = True
     ENABLE_FACE_ALIGNMENT: bool = True
 
-    # Caching (opt-in to avoid unexpected files)
-    ENABLE_CACHE: bool = False
+    ENABLE_CACHE: bool = True
     CACHE_DIR: str = ".if_cache"
 
     def __new__(cls) -> "_Config":
@@ -64,7 +63,7 @@ class _Config:
         self.FACE_MARGIN = float(os.getenv("FACE_MARGIN", "0.15"))
         self.USE_FULL_RESOLUTION = os.getenv("USE_FULL_RESOLUTION", "true").lower() in ("true", "1", "yes")
         self.ENABLE_FACE_ALIGNMENT = os.getenv("ENABLE_FACE_ALIGNMENT", "true").lower() in ("true", "1", "yes")
-        self.ENABLE_CACHE = os.getenv("ENABLE_CACHE", "false").lower() in ("true", "1", "yes")
+        self.ENABLE_CACHE = os.getenv("ENABLE_CACHE", "true").lower() in ("true", "1", "yes")
         self.CACHE_DIR = os.getenv("CACHE_DIR", ".if_cache")
 
         # Fall back to config file for non-sensitive values (API_KEY not stored here)