feat: env var overrides for Mealie/Tandoor connection settings

MEALIE_URL, MEALIE_API_KEY, TANDOOR_URL, TANDOOR_API_KEY env vars
now take priority over config.json values when set. Useful for
Kubernetes deployments where secrets are injected as env vars.

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

app/config.py

@@ -19,13 +19,26 @@ _DEFAULTS = {
     "tandoor_api_key": "",
 }
 
+# Environment variable overrides for connection settings.
+# When set, these take priority over values stored in config.json.
+_ENV_OVERRIDES = {
+    "mealie_url": os.environ.get("MEALIE_URL", "").strip().rstrip("/"),
+    "mealie_api_key": os.environ.get("MEALIE_API_KEY", "").strip(),
+    "tandoor_url": os.environ.get("TANDOOR_URL", "").strip().rstrip("/"),
+    "tandoor_api_key": os.environ.get("TANDOOR_API_KEY", "").strip(),
+}
+
 
 def _ensure_dir():
     DATA_DIR.mkdir(parents=True, exist_ok=True)
 
 
 def load() -> dict:
-    """Return the current config dict, merged with defaults."""
+    """Return the current config dict, merged with defaults.
+
+    Environment variables (MEALIE_URL, MEALIE_API_KEY, TANDOOR_URL,
+    TANDOOR_API_KEY) take priority over file-based values when set.
+    """
     cfg = dict(_DEFAULTS)
     if CONFIG_FILE.exists():
         try:
@@ -33,6 +46,10 @@ def load() -> dict:
                 cfg.update(json.load(f))
         except (json.JSONDecodeError, OSError):
             pass
+    # Apply env overrides (only non-empty values).
+    for key, val in _ENV_OVERRIDES.items():
+        if val:
+            cfg[key] = val
     return cfg