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.

frontend/lib/theme/config.ts

@@ -0,0 +1,10 @@
+import type {ThemeConfig} from "./types"
+
+/**
+ * 主题系统配置
+ * 定义主题文件的存储位置和 localStorage 键名
+ */
+export const THEME_CONFIG: ThemeConfig = {
+  styleDir: "public/style",
+  storageKey: "app-theme-id",
+}