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)

.gitea/workflows/ci.yml

@@ -0,0 +1,42 @@
+# Generated by GitHub Copilot
+#
+# ci.yml — Build and test the calorie-counter backend
+#
+# Runs on every push to main and every PR targeting main.
+# Produces a green/red signal that docker.yml waits for before building images.
+#
+# Runs on pi-runner (native ARM64) — no QEMU, no cross-compilation overhead.
+
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+# Cancel any in-progress CI run for the same ref so the single-capacity Pi
+# runner is not blocked by a superseded run.
+concurrency:
+  group: ci-${{ gitea.ref }}
+  cancel-in-progress: true
+
+jobs:
+  test:
+    name: Build & test backend
+    runs-on: pi-runner
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Java 21 LTS
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: '21'
+          cache: maven
+
+      - name: Run tests
+        working-directory: backend
+        run: mvn -q -ntp clean verify