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>

CLAUDE.md

@@ -258,6 +258,17 @@ OLLAMA_PRIMARY_MODEL=nemotron-3-nano:30b       # Model for primary server (defau
 OLLAMA_FALLBACK_MODEL=llama3.2:3b              # Model for fallback server (optional, uses primary if not set)
 SMS_API_URL=http://localhost:8000              # SMS message API endpoint (default: localhost:8000)
 SMS_API_TOKEN=your-api-token                   # SMS API authentication token (optional)
+
+# OpenRouter (Hybrid Backend) - keeps embeddings + vision local, routes chat to OpenRouter
+OPENROUTER_API_KEY=sk-or-...                   # Required to enable hybrid backend
+OPENROUTER_DEFAULT_MODEL=anthropic/claude-sonnet-4   # Used when client doesn't pick a model
+OPENROUTER_ALLOWED_MODELS=openai/gpt-4o-mini,anthropic/claude-haiku-4-5,google/gemini-2.5-flash
+                                                # Curated allowlist exposed to clients via
+                                                # GET /insights/openrouter/models. Empty = no picker.
+OPENROUTER_BASE_URL=https://openrouter.ai/api/v1     # Override base URL (optional)
+OPENROUTER_EMBEDDING_MODEL=openai/text-embedding-3-small  # Optional, embeddings stay local today
+OPENROUTER_HTTP_REFERER=https://your-site.example    # Optional attribution header
+OPENROUTER_APP_TITLE=ImageApi                  # Optional attribution header
 ```
 
 **AI Insights Fallback Behavior:**
@@ -275,6 +286,17 @@ The `OllamaClient` provides methods to query available models:
 
 This allows runtime verification of model availability before generating insights.
 
+**Hybrid Backend (OpenRouter):**
+- Per-request opt-in via `backend=hybrid` on `POST /insights/generate/agentic`.
+- Local Ollama still describes the image (vision); the description is inlined
+  into the chat prompt and the agentic loop runs on OpenRouter.
+- `request.model` (if provided) overrides `OPENROUTER_DEFAULT_MODEL` for that
+  call. The mobile picker reads from `OPENROUTER_ALLOWED_MODELS`.
+- No live capability precheck — the operator-curated allowlist is trusted.
+  A bad model id surfaces as a chat-call error.
+- `GET /insights/openrouter/models` returns `{ models, default_model, configured }`
+  for client picker UIs.
+
 ## Dependencies of Note
 
 - **actix-web**: HTTP framework