docs: define update backend api

docs/update-api.md

@@ -0,0 +1,60 @@
+ID: DOC_000006 | Version: 0.1.0 | Status: Draft
+By: Codex (GPT-5)
+
+# Update API (Kiddo Backend)
+
+## Purpose
+Definiert interne API-Endpunkte fuer Update-Status, Check, Apply, Rollback und Logs.
+
+## Endpoints
+
+### GET /update/status
+Antwort:
+```json
+{
+  "current_version": "0.1.2",
+  "last_status": "success|failed|unknown",
+  "last_error": "<optional>",
+  "last_timestamp": "2025-12-28T12:34:56Z"
+}
+```
+
+### POST /update/check
+Antwort:
+```json
+{
+  "available": true,
+  "latest_version": "0.1.3",
+  "artifact_url": "https://update.wlkns.org/kiddo/kiddo-0.1.3.tar.gz",
+  "sha256": "<hex>",
+  "message": "<optional>"
+}
+```
+
+### POST /update/apply
+Body (optional):
+```json
+{ "version": "0.1.3" }
+```
+Antwort:
+```json
+{ "started": true, "message": "update started" }
+```
+
+### POST /update/rollback
+Antwort:
+```json
+{ "started": true, "message": "rollback started" }
+```
+
+### GET /update/logs
+Antwort:
+```json
+[
+  {"timestamp":"2025-12-28T12:34:56Z","status":"success","message":"updated to 0.1.2"}
+]
+```
+
+## Notes
+- Alle Endpunkte erfordern Auth (Session/Bearer).
+- Apply/Rollback starten async; UI pollt /update/status.