feat: add nginx reverse proxy and Let's Encrypt TLS setup

- Add nginx config for SSL termination and HTTP->HTTPS redirect
- Add init-letsencrypt.sh script for automated certificate provisioning
- Update docker-compose.yml: add nginx service, expose web on internal port only
- Fix Evotor OAuth token exchange: move client credentials to form body
- Add request logging for token exchange errors
- Update BASE_URL to https://evosync.ru and set default in docker-compose
- Add refresh_token field to EvotorConnection model

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

nginx/nginx.conf

@@ -0,0 +1,32 @@
+server {
+    listen 80;
+    server_name evosync.ru www.evosync.ru;
+
+    location /.well-known/acme-challenge/ {
+        root /var/www/certbot;
+    }
+
+    location / {
+        return 301 https://$host$request_uri;
+    }
+}
+
+server {
+    listen 443 ssl;
+    server_name evosync.ru www.evosync.ru;
+
+    ssl_certificate /etc/letsencrypt/live/evosync.ru/fullchain.pem;
+    ssl_certificate_key /etc/letsencrypt/live/evosync.ru/privkey.pem;
+
+    ssl_protocols TLSv1.2 TLSv1.3;
+    ssl_ciphers HIGH:!aNULL:!MD5;
+    ssl_prefer_server_ciphers on;
+
+    location / {
+        proxy_pass http://web:8000;
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-Proto $scheme;
+    }
+}