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/send-mail-api.md

@@ -0,0 +1,67 @@
+# Send Email API
+
+## Send Email via HTTP API
+
+This is a `python` example using the `requests` library to send emails.
+
+```python
+send_body = {
+    "from_name": "Sender Name",
+    "to_name": "Recipient Name",
+    "to_mail": "Recipient Address",
+    "subject": "Email Subject",
+    "is_html": False,  # Set whether it's HTML based on content
+    "content": "<Email content: html or text>",
+}
+
+res = requests.post(
+    "http://localhost:8787/api/send_mail",
+    json=send_body, headers={
+        "Authorization": f"Bearer {your_JWT_password}",
+        # "x-custom-auth": "<your_website_password>", # If custom password is enabled
+        "Content-Type": "application/json"
+    }
+)
+
+# Using body authentication
+send_body = {
+    "token": "<your_JWT_password>",
+    "from_name": "Sender Name",
+    "to_name": "Recipient Name",
+    "to_mail": "Recipient Address",
+    "subject": "Email Subject",
+    "is_html": False,  # Set whether it's HTML based on content
+    "content": "<Email content: html or text>",
+}
+res = requests.post(
+    "http://localhost:8787/external/api/send_mail",
+    json=send_body, headers={
+        "Content-Type": "application/json"
+    }
+)
+```
+
+## Send Email via SMTP
+
+Please first refer to [Configure SMTP Proxy](/en/guide/feature/config-smtp-proxy.html).
+
+This is a `python` example using the `smtplib` library to send emails.
+
+`JWT Token Password`: This is the email login password, which can be viewed in the password menu in the UI interface.
+
+```python
+import smtplib
+
+from email.mime.text import MIMEText
+from email.mime.multipart import MIMEMultipart
+
+
+with smtplib.SMTP('localhost', 8025) as smtp:
+    smtp.login("jwt", "Enter your JWT token password here")
+    message = MIMEMultipart()
+    message['From'] = "Me <me@awsl.uk>"
+    message['To'] = "Admin <admin@awsl.uk>"
+    message['Subject'] = "Test Subject"
+    message.attach(MIMEText("Test Content", 'html'))
+    smtp.sendmail("me@awsl.uk", "admin@awsl.uk", message.as_string())
+```