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/setup.ts

@@ -1,20 +1,32 @@
 import client from './client';
 
+/** Status indicating if initial setup is required. */
 export interface SetupStatus {
   setupRequired: boolean;
 }
 
+/** Request payload for initial setup. */
 export interface SetupRequest {
   name: string;
   email: string;
   password: string;
 }
 
+/**
+ * Checks if initial setup is required.
+ * @returns Promise resolving to SetupStatus
+ * @throws {AxiosError} If the request fails
+ */
 export const getSetupStatus = async (): Promise<SetupStatus> => {
   const response = await client.get<SetupStatus>('/setup');
   return response.data;
 };
 
+/**
+ * Performs initial application setup with admin user creation.
+ * @param data - SetupRequest with admin user details
+ * @throws {AxiosError} If setup fails or already completed
+ */
 export const performSetup = async (data: SetupRequest): Promise<void> => {
   await client.post('/setup', data);
 };