fix: resolve .env.local not loading in docker compose

Fixes issue #1827 where Docker Compose wasn't properly loading .env.local file.

Problem:
- Docker Compose expects .env file for variable substitution but docs say to use .env.local
- This caused environment variables to not be loaded in Docker containers

Solution:
- Updated docker-compose.yaml to load both .env and .env.local files
- Created setup-env.sh script to help users sync .env.local to .env
- Updated documentation with clear instructions for Docker users
- Maintains backward compatibility with existing setups

Changes:
- Modified docker-compose.yaml to use array syntax for env_file
- Added scripts/setup-env.sh helper script
- Updated CONTRIBUTING.md and index.md documentation

This ensures environment variables work correctly in Docker while maintaining
the security best practice of using .env.local for sensitive data.

Contributed by: Keoma Wright

docker-compose.yaml

@@ -7,7 +7,9 @@ services:
       target: bolt-ai-production
     ports:
       - '5173:5173'
-    env_file: '.env.local'
+    env_file: 
+      - '.env'
+      - '.env.local'
     environment:
       - NODE_ENV=production
       - COMPOSE_PROFILES=production
@@ -37,7 +39,9 @@ services:
     image: bolt-ai:development
     build:
       target: bolt-ai-development
-    env_file: '.env.local'
+    env_file: 
+      - '.env'
+      - '.env.local'
     environment:
       - NODE_ENV=development
       - VITE_HMR_PROTOCOL=ws