Add Swagger/OpenAPI API docs (swagger-ui + swagger-autogen)

Generate an OpenAPI 3.0 spec from route annotations and serve it with
Swagger UI so the full REST API is browsable and testable.

- Add swagger-ui-express (runtime) and swagger-autogen (dev) deps, plus
  an `npm run swagger` script.
- server/swagger/swagger.js: generator config with API metadata, servers,
  14 tag groups, cookie + bearer security schemes, and 28 reusable
  component schemas. Follows the Express mount chain from src/app.js so
  generated paths are fully-qualified (/api/v1/...).
- Annotate every route (auth, mobile, sso, public, admin, health) with
  #swagger tags/summaries/parameters/request bodies/security and the
  actual response codes each handler returns (400/401/403/404/409/429/
  302/502, multipart uploads).
- Serve Swagger UI at /api/docs and the raw spec at /api/docs.json,
  guarded so a missing spec disables docs instead of crashing.
- Commit the generated swagger-output.json so docs work with no build
  step; swagger-autogen stays dev-only and is not needed at runtime.
- README: new "API documentation (Swagger)" section plus tech-stack and
  project-structure entries.

Covers 51 paths / 64 operations. Existing test suite (83) still passes.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/src/router/v1/auth/auth.routes.js

@@ -26,6 +26,14 @@ const loginGuards = [backoffGuard, slowLogin, loginLimiter]
 
 authRouter.post(
   '/login',
+  // #swagger.tags = ['Auth']
+  // #swagger.summary = 'Log in with username and password'
+  // #swagger.description = 'On success sets the httpOnly session cookie. If the account has 2FA enabled, returns { totpRequired, challenge } instead and no cookie is set — complete login at POST /login/totp. Rate limited and behind bot/backoff guards.'
+  /* #swagger.requestBody = { required: true, content: { "application/json": { schema: { $ref: "#/components/schemas/LoginRequest" } } } } */
+  /* #swagger.responses[200] = { description: 'Session issued, or TOTP challenge required', content: { "application/json": { schema: { $ref: "#/components/schemas/LoginResponse" } } } } */
+  /* #swagger.responses[400] = { description: 'Validation error', content: { "application/json": { schema: { $ref: "#/components/schemas/ValidationError" } } } } */
+  /* #swagger.responses[401] = { description: 'Incorrect username or password', content: { "application/json": { schema: { $ref: "#/components/schemas/Error" } } } } */
+  /* #swagger.responses[429] = { description: 'Too many attempts (rate limited / backoff)', content: { "application/json": { schema: { $ref: "#/components/schemas/Error" } } } } */
   ...loginGuards,
   body('username').isString().trim().notEmpty(),
   body('password').isString().notEmpty(),
@@ -39,6 +47,14 @@ authRouter.post(
 // Second factor: same throttling, since it's a code-guessing surface too.
 authRouter.post(
   '/login/totp',
+  // #swagger.tags = ['Auth']
+  // #swagger.summary = 'Complete login with a TOTP code'
+  // #swagger.description = 'Second step for 2FA accounts. Exchange the challenge from /login plus the current authenticator code for a session cookie.'
+  /* #swagger.requestBody = { required: true, content: { "application/json": { schema: { $ref: "#/components/schemas/TotpLoginRequest" } } } } */
+  /* #swagger.responses[200] = { description: 'Session issued', content: { "application/json": { schema: { $ref: "#/components/schemas/LoginResponse" } } } } */
+  /* #swagger.responses[400] = { description: 'Validation error', content: { "application/json": { schema: { $ref: "#/components/schemas/ValidationError" } } } } */
+  /* #swagger.responses[401] = { description: 'Invalid code or expired challenge', content: { "application/json": { schema: { $ref: "#/components/schemas/Error" } } } } */
+  /* #swagger.responses[429] = { description: 'Too many attempts (rate limited / backoff)', content: { "application/json": { schema: { $ref: "#/components/schemas/Error" } } } } */
   ...loginGuards,
   body('challenge').isString().notEmpty(),
   body('code').isString().trim().isLength({ min: 6, max: 8 }),
@@ -46,7 +62,22 @@ authRouter.post(
   loginTotp,
 )
 
-authRouter.post('/logout', logout)
-authRouter.get('/me', isLoggedIn, me)
+authRouter.post(
+  '/logout',
+  // #swagger.tags = ['Auth']
+  // #swagger.summary = 'Log out (clear the session cookie)'
+  /* #swagger.responses[200] = { description: 'Logged out', content: { "application/json": { schema: { $ref: "#/components/schemas/Message" } } } } */
+  logout,
+)
+authRouter.get(
+  '/me',
+  // #swagger.tags = ['Auth']
+  // #swagger.summary = 'Current authenticated user'
+  // #swagger.security = [{ "cookieAuth": [] }, { "bearerAuth": [] }]
+  /* #swagger.responses[200] = { description: 'The signed-in user', content: { "application/json": { schema: { type: "object", properties: { user: { $ref: "#/components/schemas/User" } } } } } } */
+  /* #swagger.responses[401] = { description: 'Not authenticated', content: { "application/json": { schema: { $ref: "#/components/schemas/Error" } } } } */
+  isLoggedIn,
+  me,
+)
 
 module.exports = authRouter