fix: re-apply dollar sign escape in docker-compose.dev.yml

Problem: Commit c2c188f (docker ports removed) accidentally reverted the
dollar sign escape fix from commit dd063d5.

Evidence:
- git show dd063d5:docker-compose.dev.yml shows: $${{project.SHARED_PROJECT_ID}} ✅
- Current docker-compose.dev.yml has: ${{project.SHARED_PROJECT_ID}} ❌
- Dokploy error log shows: 'You may need to escape any $ with another $'
- staging.yml and prod.yml still have correct $$ (lines 16-17)

Root Cause:
Manual edit in c2c188f modified docker-compose files and accidentally
removed one dollar sign during the 'docker ports removed' change.

Solution:
Re-applied dollar sign escape: $ → $$ on lines 14-15

Verification:
- grep "SHARED_PROJECT_ID" docker-compose.*.yml shows all have $${{
- docker-compose.dev.yml now matches staging.yml and prod.yml

This will fix the Dokploy deployment error.

docker-compose.dev.yml

@@ -11,8 +11,8 @@ services:
       - STACK_DOMAIN_SUFFIX=${STACK_DOMAIN_SUFFIX:-ai.flexinit.nl}
       - STACK_IMAGE=${STACK_IMAGE:-git.app.flexinit.nl/flexinit/agent-stack:latest}
       - RESERVED_NAMES=${RESERVED_NAMES:-admin,api,www,root,system,test,demo,portal}
-      - SHARED_PROJECT_ID=${{project.SHARED_PROJECT_ID}}
-      - SHARED_ENVIRONMENT_ID=${{project.SHARED_ENVIRONMENT_ID}}
+      - SHARED_PROJECT_ID=$${{project.SHARED_PROJECT_ID}}
+      - SHARED_ENVIRONMENT_ID=$${{project.SHARED_ENVIRONMENT_ID}}
     env_file:
       - .env
     restart: unless-stopped