fix: make Redis non-fatal in production to prevent crash loop on Cloud Run

Redis init was raising RuntimeError in production, causing Gunicorn worker
crash loop when Memorystore connection fails during cold start. Now logs
error but continues — app runs in degraded mode without Redis (no cache,
no pub/sub, dashboard uses DB fallback).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: mangod12

backend/app/core/redis_client.py

@@ -23,13 +23,10 @@ async def init_redis():
         _redis_client = client
         logger.info("Connected to Redis at %s", settings.REDIS_URL)
     except Exception as exc:
-        if settings.APP_ENV.lower() == "production":
-            logger.error("Redis connection failed in production: %s", exc)
-            raise RuntimeError(
-                f"Redis is required in production but unavailable: {exc}"
-            ) from exc
+        logger.error("Redis connection failed: %s", exc)
 
-        logger.warning("Redis not available — trying fakeredis for local dev")
+        if settings.APP_ENV.lower() != "production":
+            logger.warning("Trying fakeredis for local dev")
         try:
             import fakeredis.aioredis as fakeredis_mod