docs: update documentation to OKF v0.1 format

docs/api/rest-overview.md

@@ -3,7 +3,7 @@ type: api
 title: REST API Overview
 description: Base URL, versioning, auth, CSRF, and the standard error envelope.
 tags: [api, rest, overview, csrf]
-timestamp: 2026-07-21T22:19:08Z
+timestamp: 2026-07-23T00:10:00Z
 ---
 
 # Base URL & versioning
@@ -78,7 +78,18 @@ endpoint). Full list lives in `backend/src/common/errors/error-codes.ts`:
 `CSRF_INVALID`, `WEAK_PASSWORD`, `USERNAME_TAKEN`,
 `INVALID_CREDENTIALS`, `TOKEN_REVOKED`, `THEME_INVALID`,
 `REGISTRATIONS_DISABLED`, `INVALID_OLD_PASSWORD`, `PASSWORD_POLICY`,
-`PASSWORDS_DO_NOT_MATCH`, `INTERNAL`.
+`PASSWORDS_DO_NOT_MATCH`, `CATEGORY_HAS_CHALLENGES`, `SYSTEM_PROTECTED`,
+`CHALLENGE_NAME_TAKEN`, `CHALLENGE_INVALID_CATEGORY`,
+`CHALLENGE_INVALID_POINTS`, `CHALLENGE_INVALID_PORT`,
+`CHALLENGE_INVALID_IP`, `CHALLENGE_FILE_LIMIT`,
+`IMPORT_VALIDATION_FAILED`, `IMPORT_PARTIAL_FAILURE`,
+`EVENT_NOT_RUNNING`, `FLAG_INCORRECT`, `CHALLENGE_DISABLED`, `INTERNAL`.
+
+The player-facing codes (`EVENT_NOT_RUNNING`, `FLAG_INCORRECT`) are
+emitted by the challenges submit endpoint; see
+[Challenges Endpoints](/api/challenges.md) for the full set of HTTP
+statuses and the canonical messages produced by
+`messageForSolveError`.
 
 # See also
 
@@ -86,4 +97,5 @@ endpoint). Full list lives in `backend/src/common/errors/error-codes.ts`:
 - [Admin Endpoints](/api/admin.md)
 - [Setup Endpoint](/api/setup.md)
 - [System Endpoints](/api/system.md)
-- [Uploads Endpoints](/api/uploads.md)
+- [Uploads Endpoints](/api/uploads.md)
+- [Challenges Endpoints](/api/challenges.md)