refactor(repo): consolidate openflare-server to root and move subprojects to internal/apps

- Merge all files inside openflare-server to the repository root directory.
- Relocate agent, relay, and flared subprojects from internal/ to internal/apps/.
- Combine docker-compose files and update build context paths to root.
- Update GitHub workflows and Dockerfiles to refer to new directories and package names.
- Rewrite Go package imports across all files.
- Resolve database renew test race condition and clean up docs.

.github/workflows/docker-server.yml

@@ -74,7 +74,7 @@ jobs:
         id: build
         uses: docker/build-push-action@v7
         with:
-          context: ./openflare-server
+          context: .
           file: ./docker/Dockerfile
           platforms: ${{ matrix.platform }}
           outputs: type=image,name=${{ env.IMAGE }},push-by-digest=true,name-canonical=true,push=true