chore: implement instruction compliance remediation

- Replace Go interface{} with any (Go 1.18+ standard)
- Add database indexes to frequently queried model fields
- Add JSDoc documentation to frontend API client methods
- Remove deprecated docker-compose version keys
- Add concurrency groups to all 25 GitHub Actions workflows
- Add YAML front matter and fix H1→H2 headings in docs

Coverage: Backend 85.5%, Frontend 87.73%
Security: No vulnerabilities detected

Refs: docs/plans/instruction_compliance_spec.md

frontend/src/api/docker.ts

@@ -1,11 +1,13 @@
 import client from './client'
 
+/** Docker port mapping information. */
 export interface DockerPort {
   private_port: number
   public_port: number
   type: string
 }
 
+/** Docker container information. */
 export interface DockerContainer {
   id: string
   names: string[]
@@ -17,7 +19,15 @@ export interface DockerContainer {
   ports: DockerPort[]
 }
 
+/** Docker API client for container operations. */
 export const dockerApi = {
+  /**
+   * Lists Docker containers from a local or remote host.
+   * @param host - Optional Docker host address
+   * @param serverId - Optional remote server ID
+   * @returns Promise resolving to array of DockerContainer objects
+   * @throws {AxiosError} If listing fails or host unreachable
+   */
   listContainers: async (host?: string, serverId?: string): Promise<DockerContainer[]> => {
     const params: Record<string, string> = {}
     if (host) params.host = host