Add --ensure flag to load-env.js that skips generation if
env.generated.ts already exists, allowing ng serve to work in
fresh worktrees without running npm run env first.
Also make load-env.js idempotent by comparing content before
writing and removing the timestamp from generated output.
- Add getEnvOptional() method for accessing optional environment variables
- Separate REQUIRED_ENV_KEYS from OPTIONAL_ENV_KEYS in load-env.js
- Update UnsplashService to use getEnvOptional() instead of getEnv()
- ENV object now only contains actual values, not 'undefined' strings
- Cleaner separation between required and optional configuration
- Always read system environment variables first, then override with .env file
- Ensure all required keys are always present in generated types
- Pass environment variables correctly in Docker build
- Update .dockerignore to exclude build artifacts
