fix: set explicit hostname for supabase-pooler (Erlang DNS fix)

Supavisor (Erlang/Elixir) cannot start if it cannot resolve its own
hostname. Setting a fixed hostname solves the name resolution failure.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

infrastructure/docker-compose.override.yml

@@ -27,6 +27,10 @@ services:
       - default
       - proxy
 
+  # Pooler: fixer Hostname damit Erlang-VM den eigenen Namen auflösen kann
+  supabase-pooler:
+    hostname: supabase-pooler
+
   # Nightly Scheduler: APNs-Ping + Resonance-Milestones
   # ⚠️  APNs: erfordert bezahlten Apple Developer Account ($99/Jahr)
   scheduler: