docs: warn that COMPOSE_FILE uses ';' on Windows, ':' on Linux/macOS

Windows users following the docs hit "The system cannot find the file
specified" because COMPOSE_FILE's separator is OS-specific (':' collides
with the C: drive letter). Fix every Windows example to use ';', add an
explicit OS-separator warning in .env.example, README, DEPLOY.md and the
gpu-windows compose comment, and point users at the explicit `-f` form as
a separator-agnostic alternative.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

docker-compose.gpu-windows.yml

@@ -5,8 +5,9 @@
 #
 #   docker compose -f docker-compose.yml -f docker-compose.gpu-windows.yml up -d
 #
-# Or set COMPOSE_FILE in .env (recommended):
-#   COMPOSE_FILE=docker-compose.yml:docker-compose.gpu-windows.yml
+# Or set COMPOSE_FILE in .env (note the ";" separator on Windows — ":" collides
+# with the C: drive letter and breaks file resolution):
+#   COMPOSE_FILE=docker-compose.yml;docker-compose.gpu-windows.yml
 services:
   ollama:
     deploy: