Add shared bash utility library to reduce script duplication

[PAMulligan]

Summary

25+ shell scripts duplicate common patterns: color output, logging, error handling, dependency checks, JSON parsing. A shared utility library would reduce duplication and improve consistency.

Duplicated Patterns

• Color/formatting helpers (RED, GREEN, BOLD, etc.)
• command -v checks for required tools
• JSON output formatting
• Exit code handling and error reporting
• Temp file/directory management
• Script header/banner printing

Acceptance Criteria

• scripts/lib/common.sh with shared bash functions
• scripts/lib/colors.sh for terminal color helpers
• Existing scripts refactored to source shared libs
• Consistent error output format across all scripts
• Shared Node.js utilities in scripts/lib/ for JSON operations