🐛 Add WAL volume mount for Loki 3.0

Fixes "mkdir wal: read-only file system" error by adding dedicated
emptyDir volume for Loki's Write-Ahead Log.

Loki 3.0 requires writable filesystem for WAL when using ingester.
The deployment has readOnlyRootFilesystem: true for security, so we
mount a writable emptyDir at /wal specifically for this purpose.

Changes:
- Added /wal volume mount to Loki container
- Added wal emptyDir volume to pod spec

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

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

Author: Ladas

components/02-observability/loki/deployment.yaml

@@ -88,6 +88,8 @@ spec:
           readOnly: true
         - name: storage
           mountPath: /loki
+        - name: wal
+          mountPath: /wal
 
         securityContext:
           allowPrivilegeEscalation: false
@@ -102,3 +104,5 @@ spec:
           name: loki-config
       - name: storage
         emptyDir: {}
+      - name: wal
+        emptyDir: {}