feat: Raspberry Pi deployment — Dockerfile, CI/CD workflows, actuator

Backend:
- backend/Dockerfile: multi-stage build (local + ci-image targets)
  - eclipse-temurin:21-jre-alpine runtime, non-root user caloriecounter
  - DOCKER_BUILDKIT=0 + native JAR build pattern for ARM64 Pi runner
- pom.xml: add spring-boot-starter-actuator
- application.yml: expose /actuator/health (liveness probe for Docker healthcheck)

CI/CD:
- .gitea/workflows/ci.yml: Maven test on pi-runner (push + PR)
- .gitea/workflows/docker.yml: build + push calorie-counter-api:latest/:sha
  - Triggers after CI passes (workflow_run) to avoid OOM on single-capacity Pi
  - Docker login before Maven build (avoids daemon timeout after heavy CPU)
  - Deploys immediately via docker.sock to /home/andris/homelab/calorie-counter/

Mobile:
- api.ts: update baseURL default to https://calories.amlab.dev
  (LAN fallback: http://10.18.1.135:8085 via WireGuard)

Homelab changes pushed directly via Gitea MCP:
- homelab/calorie-counter/docker-compose.yml (port 8085, 120s start_period)
- homelab/calorie-counter/.env.example
- homelab/.gitea/workflows/deploy-calorie-counter.yml (cron every 10 min)
- homelab/backup/backup.sh (added calorie-counter pg_dump)

backend/pom.xml

@@ -86,6 +86,12 @@
             <artifactId>spring-boot-starter-webflux</artifactId>
         </dependency>
 
+        <!-- Actuator — liveness/readiness probes for Docker healthcheck -->
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-actuator</artifactId>
+        </dependency>
+
         <!-- Test -->
         <dependency>
             <groupId>org.springframework.boot</groupId>