chore: add api docs (#1965)

docs/api/tag.md

@@ -0,0 +1,84 @@
+# Tag APIs
+
+## Create Tag
+
+```
+POST /api/v1/tag
+```
+
+**Request Body**
+
+```json
+{
+  "name": "python"
+}
+```
+
+**Response**
+
+```
+"python"
+```
+
+**Status Codes**
+
+- 200: Created
+- 400: Invalid request
+- 500: Internal server error
+
+## Get Tag List
+
+```
+GET /api/v1/tag
+```
+
+**Response**
+
+```json
+["python", "golang", "javascript"]
+```
+
+**Status Codes**
+
+- 200: OK
+- 401: Unauthorized
+- 500: Internal server error
+
+## Suggest Tags
+
+```
+GET /api/v1/tag/suggestion
+```
+
+**Response**
+
+```json
+["django", "flask", "numpy"]
+```
+
+**Status Codes**
+
+- 200: OK
+- 401: Unauthorized
+- 500: Internal server error
+
+## Delete Tag
+
+```
+POST /api/v1/tag/delete
+```
+
+**Request Body**
+
+```json
+{
+  "name": "outdated_tag"
+}
+```
+
+**Status Codes**
+
+- 200: Deleted
+- 400: Invalid request
+- 401: Unauthorized
+- 500: Internal server error