chore: replace Promtail with Grafana Alloy for log collection (refs #97)

Promtail 2.9.0 embeds Docker client API v1.42 which is incompatible with
Docker Engine v29 (minimum API v1.44). Grafana Alloy v1.12.2 resolves this
by using a compatible Docker client.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -286,16 +286,20 @@ services:
         max-size: "10m"
         max-file: "3"
 
-  # Log Aggregation - Promtail
-  mvp-promtail:
-    image: ${REGISTRY_MIRRORS:-git.motovaultpro.com/egullickson/mirrors}/grafana/promtail:2.9.0
-    container_name: mvp-promtail
+  # Log Aggregation - Alloy (replaces Promtail)
+  mvp-alloy:
+    image: ${REGISTRY_MIRRORS:-git.motovaultpro.com/egullickson/mirrors}/grafana/alloy:v1.12.2
+    container_name: mvp-alloy
     restart: unless-stopped
     volumes:
-      - ./config/promtail/config.yml:/etc/promtail/config.yml:ro
+      - ./config/alloy/config.alloy:/etc/alloy/config.alloy
       - /var/lib/docker/containers:/var/lib/docker/containers:ro
       - /var/run/docker.sock:/var/run/docker.sock:ro
-    command: -config.file=/etc/promtail/config.yml
+    command:
+      - run
+      - --server.http.listen-addr=0.0.0.0:12345
+      - --storage.path=/var/lib/alloy/data
+      - /etc/alloy/config.alloy
     networks:
       - backend
     depends_on: