docs(readme): update API URL to HTTPS domain, add deployment/SSL/traffic info

README.md

@@ -33,6 +33,14 @@ python app.py
 - Web UI: http://localhost:5000
 - API: see /api/upload and /api/file endpoints
 
+Deployment
+
+The production instance runs at:
+- **Domain**: `xiaji-temp.duckdns.org`
+- **HTTPS**: Let's Encrypt SSL with auto-renewal (certbot timer)
+- **Nginx**: reverse proxy with 500MB upload limit, 80→443 redirect
+- **Gunicorn**: 4 workers, systemd-managed
+
 Project layout
 - app.py               # Flask application
 - config.py            # Configuration constants
@@ -57,6 +65,16 @@ Expiry and cleanup
 - A cleanup operation removes expired files from disk and deletes DB rows
 - Cleanup is invoked on access endpoints (and can be wired to a cron/daemon later)
 
+Traffic limits
+- Maximum file size: 500 MB
+- Per-IP daily traffic limit: 20 GB (upload + download combined)
+- IP traffic tracked in SQLite `ip_traffic` table, reset daily
+
+SSL certificate
+- Let's Encrypt certificate deployed via certbot
+- Auto-renewal via systemd timer: `certbot.timer`
+- Manual renewal test: `certbot renew --dry-run`
+
 Security notes
 - Do not commit secrets. Secrets should be provided via environment variables in production.
 - This repository currently avoids embedding credentials.
@@ -76,7 +94,7 @@ Upload a file via the API endpoint:
 ```python
 import requests
 
-BASE_URL = "http://23.226.133.121:5000"
+BASE_URL = "https://xiaji-temp.duckdns.org"
 
 expiry = "24h"  # 1h, 24h, 7d
 
@@ -103,7 +121,7 @@ Response format:
     "filename": "file.zip",
     "filesize": 1048576,
     "expiry_hours": 24,
-    "share_url": "http://23.226.133.121:5000/file/550e8400..."
+    "share_url": "https://xiaji-temp.duckdns.org/file/550e8400..."
 }
 ```
 
@@ -122,10 +140,6 @@ Or use the bundled client script:
 python upload_client.py /path/to/file.zip 24h
 ```
 
-Limits
-- Maximum file size: 500 MB
-- Per-IP daily traffic limit: 20 GB (upload + download combined)
-
 Contributing
 - Pull requests are welcome. Please follow the project style and ensure tests pass.