When installation fails in default (clean) mode, show a helpful error
message suggesting users run with --debug flag for detailed output.

Features:
- Clear error indication with emoji
- Actionable troubleshooting advice
- Maintains clean UX while providing debugging path
- Applied to critical Docker Compose operations

This helps users quickly identify and resolve installation issues.

Address all 6 issues identified in Copilot review:

1. Add signal traps to prevent process leaks on interruption
2. Fix race condition in exit status handling with explicit STATUS check
3. Apply consistent progress suppression to database creation step
4. Suppress docker compose up output in non-debug mode for consistency
5. Use consistent comparison operators (x = xyes pattern)
6. Preserve error messages using temporary files while suppressing progress

Key improvements:
- Robust background process management with proper cleanup
- Complete progress output suppression in clean mode
- Error details automatically shown on failure (--debug less critical)
- Maintains clean UX while providing excellent troubleshooting info

Address cubic-dev-ai feedback: docker compose up -d now captures and
displays error details consistently with other docker operations.

Previously:
- docker compose pull/run: captured errors to temp file, displayed details
- docker compose up -d: discarded all error output (>/dev/null 2>&1)

Now all docker operations consistently capture and display error details
while maintaining clean progress output in non-debug mode.

Address Copilot feedback on code duplication:

- Extract repeated progress display pattern into run_with_progress() function
- Eliminates 40+ lines of duplicated code between pull and create_db operations
- Fixes ERROR_LOG variable reuse issue with proper scoping
- Improves maintainability and reduces bug risk
- Each operation now uses independent ERROR_LOG variables

This refactoring maintains identical functionality while significantly
improving code quality and maintainability.

Address remaining Copilot feedback:

- Reorder help text to match usage line order for better readability
- Capture script name at startup to handle symlinks and different invocations
- Use SCRIPT_NAME variable in error messages and help text for consistency

These improvements enhance user experience and ensure correct script
references regardless of how the script is invoked.

Address cubic-dev-ai feedback on POSIX compliance:

- Remove 'local' keyword which is a bashism, not POSIX-compliant
- Use unique variable names (RWP_MESSAGE, RWP_COMMAND) instead
- Maintains compatibility with strict POSIX shells
- Script continues to use #!/usr/bin/env sh as intended

This ensures the script works on all POSIX-compliant shells,
not just bash and dash.