fix: address code review findings

- Create README.md with project overview, quick start, Docker deployment, CI/CD info
- Update CLAUDE.md with Deployment section
- Fix cmd/api/main.go to use REDIS_ADDR env var with fallback
- Fix Dockerfile to use golang:1.22-alpine instead of golang:1.26-alpine
- Fix .gitea/workflows/deploy.yml to include Docker registry prefix in image tags

.gitea/workflows/deploy.yml

@@ -47,5 +47,5 @@ jobs:
           context: .
           push: true
           tags: |
-            latest
-            ${{ github.sha }}
+            ${{ secrets.DOCKER_USERNAME }}/trip-planner:latest
+            ${{ secrets.DOCKER_USERNAME }}/trip-planner:${{ github.sha }}