feat(geoportal): N8N webhook on sync completion + tile cache monitoring

- weekend-deep-sync.ts: fire webhook to N8N_WEBHOOK_URL after each sync cycle
  (N8N triggers tippecanoe PMTiles rebuild via SSH on host)
- nginx tile-cache: add stub_status at /status, custom log format with cache status
- Add tile-cache-stats.sh: shows HIT/MISS ratio, cache size, slow tiles
- docker-compose: add N8N_WEBHOOK_URL env var

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

nginx/tile-cache.conf

@@ -8,7 +8,13 @@ proxy_cache_path /var/cache/nginx/tiles
   inactive=7d
   use_temp_path=off;
 
+# Log format with cache status for monitoring (docker logs tile-cache | grep HIT/MISS)
+log_format tiles '$remote_addr [$time_local] "$request" $status '
+                 'cache=$upstream_cache_status size=$body_bytes_sent '
+                 'time=$request_time';
+
 server {
+  access_log /var/log/nginx/access.log tiles;
   listen 80;
   server_name _;
 
@@ -19,6 +25,12 @@ server {
     add_header Content-Type text/plain;
   }
 
+  # nginx status (active connections, request counts) — for monitoring
+  location = /status {
+    access_log off;
+    stub_status on;
+  }
+
   # Martin catalog endpoint (no cache)
   location = /catalog {
     proxy_pass http://martin:3000/catalog;