Improve CONTRIBUTING.md with architecture guide and good-first-issue links

[roeimichael]

Problem

CONTRIBUTING.md lists broad areas where help is welcome but does not:

• Link to GitHub issues labeled "good first issue"
• Explain the data flow architecture for newcomers
• Mention the architecture docs in docs/phase1-architecture.md and docs/phase2-architecture.md
• Suggest a reading order for understanding the codebase

What to do

Add a "Start Here" section to CONTRIBUTING.md that includes:

1. Architecture overview — brief description of the data flow:
   ```
   Claude Code Hooks → FastAPI Collector → Delta Engine → Anomaly Detection → Notifications
   ```
2. Recommended reading order for new contributors:
   • `config.py` → `models.py` → `delta_engine.py` → `anomaly.py`
3. Links to architecture docs: `docs/phase1-architecture.md`, `docs/phase2-architecture.md`
4. Link to good first issues: `https://github.com/roeimichael/ContextAnalyzerTerminal/labels/good%20first%20issue\`

Why this is a good first issue

It's a documentation-only change — perfect for getting familiar with the project structure before diving into code.

[18mukeshram]

Hi, I’d like to work on this issue.

I have experience building full-stack systems with clear architecture and documentation, and I’m comfortable understanding data flow and structuring contributor guides.

I can take care of adding a "Start Here" section with architecture overview, reading order, and useful links for new contributors.

Please let me know if this is available. Thanks!

[18mukeshram]

Hi, I’ve submitted a PR for this issue: #22. Please take a look when you get a chance. Thanks!

[ishan4432]

Hi, I’d like to work on this issue. I can improve the CONTRIBUTING.md by adding clear steps and structure.