feat: add daily request limit and refactor access control (#759)

- Add daily request limit per IP in blacklist settings (1-1,000,000/day)
- Refactor access control logic: merge blacklist and rate limit checks
- Remove RATE_LIMIT_API_DAILY_REQUESTS env var, use database config instead
- Move x-custom-auth check earlier in middleware chain
- Add comprehensive English documentation (31 new guide pages)
- Improve code structure and error handling

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-authored-by: Claude <noreply@anthropic.com>

vitepress-docs/docs/en/guide/feature/mail-api.md

@@ -0,0 +1,66 @@
+# Mail API
+
+## Viewing Emails via Mail API
+
+This is a `python` example using the `requests` library to view emails.
+
+```python
+limit = 10
+offset = 0
+res = requests.get(
+    f"https://<your-worker-address>/api/mails?limit={limit}&offset={offset}",
+    headers={
+        "Authorization": f"Bearer {your-JWT-password}",
+        # "x-custom-auth": "<your-website-password>", # If custom password is enabled
+        "Content-Type": "application/json"
+    }
+)
+```
+
+## Admin Mail API
+
+Supports `address` filter and `keyword` filter
+
+```python
+import requests
+
+url = "https://<your-worker-address>/admin/mails"
+
+querystring = {
+    "limit":"20",
+    "offset":"0",
+    # address and keyword are optional parameters
+    "address":"xxxx@awsl.uk",
+    "keyword":"xxxx"
+}
+
+headers = {"x-admin-auth": "<your-Admin-password>"}
+
+response = requests.get(url, headers=headers, params=querystring)
+
+print(response.json())
+```
+
+## User Mail API
+
+Supports `address` filter and `keyword` filter
+
+```python
+import requests
+
+url = "https://<your-worker-address>/user_api/mails"
+
+querystring = {
+    "limit":"20",
+    "offset":"0",
+    # address and keyword are optional parameters
+    "address":"xxxx@awsl.uk",
+    "keyword":"xxxx"
+}
+
+headers = {"x-admin-auth": "<your-Admin-password>"}
+
+response = requests.get(url, headers=headers, params=querystring)
+
+print(response.json())
+```