fix(docker): configure Loki tmpfs with correct UID for non-root operation

Loki 3.0.0 runs as a non-root user (UID 10001) by default. The tmpfs
mount at /loki must be owned by this user for Loki to write its data.

Solution: Set tmpfs uid=10001,gid=10001 to match the Loki container user.
This approach maintains non-root security posture matching K8s deployments.

Also ensure loki-config.yaml has world-readable permissions (mode 644)
so the non-root Loki user can read the mounted config file.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: vishnu2kmohan

docker-compose.test.yml

@@ -635,7 +635,8 @@ services:
     volumes:
       - ./docker/loki/loki-config.yaml:/etc/loki/local-config.yaml:ro
     tmpfs:
-      - /loki:rw,noexec,nosuid,size=256m
+      # UID 10001 is the loki user in grafana/loki:3.0.0
+      - /loki:rw,noexec,nosuid,size=256m,uid=10001,gid=10001
     healthcheck:
       test: ["CMD", "wget", "--spider", "-q", "http://localhost:3100/ready"]
       interval: 10s