feat(HRT-200): AI Router — Multi-provider LLM routing with failover

- 4 provider adapters: OpenAI (SDK), Anthropic (SDK), Google (google-genai), Mistral (direct HTTP)
- Core router with automatic failover + exponential backoff
- Flask blueprint with /api/v1/ai/* endpoints
- Auth via token-broker verify endpoint
- DB models for ai_providers, ai_model_mapping, ai_router_log
- /health endpoint (parallel provider check), /usage stats
- 21 unit tests (all passing)

ai_router_api.py

@@ -0,0 +1,77 @@
+#!/usr/bin/env python3
+"""
+AI Router API — Multi-provider LLM routing with failover
+Port: 8783 | DB: SQLite ai_router.db
+HRT-200 — AI Router (Multi-provider + failover)
+
+Endpoints:
+  GET    /api/v1/ai/health              — Check all providers health
+  GET    /api/v1/ai/models              — List available models
+  POST   /api/v1/ai/chat                — Chat completion with auto-failover
+  GET    /api/v1/ai/admin/providers     — List configured providers
+  POST   /api/v1/ai/admin/providers     — Upsert a provider
+  POST   /api/v1/ai/admin/model-mappings— Upsert a model mapping
+  DELETE /api/v1/ai/admin/providers/:id — Remove a provider
+  GET    /api/v1/ai/usage               — Usage logs
+  GET    /api/v1/ai/usage/summary       — Aggregated usage stats
+"""
+
+import logging
+import logging.handlers
+import os
+import sys
+
+from flask import Flask, jsonify
+from flask_cors import CORS
+
+LOG_DIR = os.path.join(os.path.dirname(__file__), "ai_router", "logs")
+os.makedirs(LOG_DIR, exist_ok=True)
+
+logging.basicConfig(
+    level=logging.INFO,
+    format="%(asctime)s [%(levelname)s] ai-router: %(name)s: %(message)s",
+    handlers=[
+        logging.StreamHandler(sys.stdout),
+        logging.handlers.RotatingFileHandler(
+            os.path.join(LOG_DIR, "ai_router.log"),
+            maxBytes=5 * 1024 * 1024,
+            backupCount=3,
+        ),
+    ],
+)
+logger = logging.getLogger("ai_router")
+
+PORT = int(os.environ.get("AI_ROUTER_PORT", "8783"))
+
+
+def create_app():
+    app = Flask(__name__)
+    CORS(app)
+
+    from ai_router.api import register_ai_router
+    from ai_router.models import init_db
+
+    init_db()
+    register_ai_router(app)
+
+    @app.errorhandler(404)
+    def not_found(e):
+        return jsonify({"error": "not_found", "message": "Route not found"}), 404
+
+    @app.errorhandler(500)
+    def internal_error(e):
+        logger.error(f"Internal error: {e}")
+        return jsonify({"error": "internal_error", "message": "Internal server error"}), 500
+
+    return app
+
+
+if __name__ == "__main__":
+    logger.info("=" * 60)
+    logger.info("AI Router API starting...")
+    logger.info(f"Port: {PORT}")
+    logger.info("=" * 60)
+
+    app = create_app()
+    debug = os.environ.get("FLASK_ENV", "production") == "development"
+    app.run(host="0.0.0.0", port=PORT, debug=debug)