fix search runs with empty results

src/nsct/config.py

@@ -62,6 +62,10 @@ class AppSettings(BaseModel):
     postgres: DatabaseConfig = Field(default_factory=DatabaseConfig)
     debug: bool = Field(default=False)
     searxng_base_url: str | None = Field(default=None, description="SearXNG instance URL.")
+    searxng_engines: tuple[str, ...] = Field(
+        default=(),
+        description="Optional allow-list of SearXNG engines for web searches.",
+    )
 
     @staticmethod
     def from_env() -> "AppSettings":
@@ -98,6 +102,11 @@ class AppSettings(BaseModel):
 
         debug = os.environ.get("NSCT_DEBUG", "false").lower() == "true"
         searxng_url = os.environ.get("NSCT_SEARXNG_BASE_URL", None)
+        searxng_engines = tuple(
+            engine.strip()
+            for engine in os.environ.get("NSCT_SEARXNG_ENGINES", "").split(",")
+            if engine.strip()
+        )
 
         return AppSettings(
             llm=llm_cfg,
@@ -106,6 +115,7 @@ class AppSettings(BaseModel):
             postgres=postgres_cfg,
             debug=debug,
             searxng_base_url=searxng_url,
+            searxng_engines=searxng_engines,
         )
 
     @property
@@ -113,4 +123,4 @@ class AppSettings(BaseModel):
         """Return a config directory path for persisting runtime data."""
         data_dir = Path.home() / ".nsct"
         data_dir.mkdir(parents=True, exist_ok=True)
-        return data_dir
+        return data_dir