servers/psmf: add psmf server docs, nginx/tailscale config, and data-sync

Document the psmf host (DNS, second tailscale netns instance, nginx
vhosts, migration plan) and add the docker-dev-22 psmf-data-sync
service plus the storage-23 pg_hba.conf entry it needs.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

servers/psmf/files/nginx/default

@@ -0,0 +1,28 @@
+# Reverse proxy: horst-2 default site -> horst-1 Apache (10.0.0.5)
+# Deployed during the horst-1 -> horst-2 migration.
+# See servers/psmf/migration-plan.md.
+
+server {
+    listen 80 default_server;
+    listen [::]:80 default_server;
+
+    server_name _;
+
+    # Long bodies / uploads from the legacy PHP intranet app.
+    client_max_body_size 64m;
+
+    location / {
+        proxy_pass http://10.0.0.5;
+
+        proxy_http_version 1.1;
+        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;
+        proxy_set_header X-Forwarded-Host  $host;
+
+        proxy_connect_timeout 10s;
+        proxy_read_timeout    300s;
+        proxy_send_timeout    300s;
+    }
+}