Fix settings override bug: allow False and 0 from database

Fixes #217 - Database values of False and 0 are now properly respected
instead of being ignored. Removed 'and v' check that incorrectly treated
these legitimate config values as 'empty'. Now only truly empty values
(None, empty string, empty list, empty dict) are ignored in favor of env.

routstr/core/settings.py

@@ -235,7 +235,7 @@ class SettingsService:
 
             merged_dict: dict[str, Any] = dict(env_resolved.dict())
             merged_dict.update(
-                {k: v for k, v in db_json.items() if v not in (None, "", []) and v}
+                {k: v for k, v in db_json.items() if v not in (None, "", [], {})}
             )
 
             # Ensure primary_mint is consistent with cashu_mints if not explicitly set