[FEATURE] Add pentest depth option (Quick / Standard / Deep) to CLI

[0xallam]

Introduce a --depth CLI flag to allow users to control scan depth vs speed.

Proposed modes:

• Quick - optimized for CI/CD and fast checks
• Standard - default mode for routine manual runs and ad-hoc assessments
• Deep - for more thorough security reviews

Requirements:

• Map each mode to:
  • Agent iteration limits
  • Fuzzing aggressiveness
  • Timeout thresholds
  • Number of parallel agents/tools
• Add docs + CLI examples in the README / docs site