Fix Docker segfault on Apple Silicon — add linux/arm64 platform

Go runtime netpoll_epoll segfaults under amd64 emulation on ARM Macs.
Explicitly target arm64 for all build services.

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

docker-compose.yml

@@ -40,6 +40,7 @@ services:
 
   # Casera API
   api:
+    platform: linux/arm64
     build:
       context: .
       target: api
@@ -101,6 +102,7 @@ services:
 
   # Casera Admin Panel (Next.js)
   admin:
+    platform: linux/arm64
     build:
       context: .
       target: admin
@@ -125,6 +127,7 @@ services:
 
   # Casera Worker (Background Jobs)
   worker:
+    platform: linux/arm64
     build:
       context: .
       target: worker