feat(ai): curated OpenRouter model picker for hybrid backend

Add OPENROUTER_ALLOWED_MODELS env var and GET /insights/openrouter/models
endpoint returning the curated list verbatim. Drop the live capability
precheck in hybrid mode — trust the operator's allowlist; bad ids surface
as a chat-call error.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ai/handlers.rs

@@ -445,6 +445,34 @@ pub async fn get_available_models_handler(
     HttpResponse::Ok().json(response)
 }
 
+#[derive(Debug, Serialize)]
+pub struct OpenRouterModelsResponse {
+    pub models: Vec<String>,
+    pub default_model: Option<String>,
+    pub configured: bool,
+}
+
+/// GET /insights/openrouter/models - Curated OpenRouter model ids exposed
+/// to clients for the hybrid backend. Returned verbatim from
+/// `OPENROUTER_ALLOWED_MODELS`; no live call to OpenRouter.
+#[get("/insights/openrouter/models")]
+pub async fn get_openrouter_models_handler(
+    _claims: Claims,
+    app_state: web::Data<crate::state::AppState>,
+) -> impl Responder {
+    let configured = app_state.openrouter.is_some();
+    let default_model = app_state
+        .openrouter
+        .as_ref()
+        .map(|c| c.primary_model.clone());
+    let response = OpenRouterModelsResponse {
+        models: app_state.openrouter_allowed_models.clone(),
+        default_model,
+        configured,
+    };
+    HttpResponse::Ok().json(response)
+}
+
 /// POST /insights/rate - Rate an insight (thumbs up/down for training data)
 #[post("/insights/rate")]
 pub async fn rate_insight_handler(