feat(ai): add OpenRouter provider order and fallback controls

app/core/config.py

@@ -69,6 +69,14 @@ class Settings(BaseSettings):
         description="Premium Llama model identifier",
     )
     OPENROUTER_TIMEOUT: int = Field(default=30, description="OpenRouter API timeout in seconds")
+    OPENROUTER_PROVIDER_ORDER: List[str] = Field(
+        default=["NovitaAI", "AkashML", "Inception"],
+        description="Preferred OpenRouter providers in priority order",
+    )
+    OPENROUTER_ALLOW_PROVIDER_FALLBACKS: bool = Field(
+        default=True,
+        description="Allow OpenRouter to fallback outside preferred providers",
+    )
 
     # WordPress Integration
     WORDPRESS_API_URL: str = Field(
@@ -103,6 +111,14 @@ class Settings(BaseSettings):
             return [origin.strip() for origin in v.split(",") if origin.strip()]
         return v
 
+    @field_validator("OPENROUTER_PROVIDER_ORDER", mode="before")
+    @classmethod
+    def parse_provider_order(cls, v: Union[str, List[str]]) -> List[str]:
+        """Parse comma-separated OpenRouter provider list into array."""
+        if isinstance(v, str):
+            return [provider.strip() for provider in v.split(",") if provider.strip()]
+        return v
+
 
 # Global settings instance
 _settings: Union[Settings, None] = None