Update Nielsen's Heuristics and future phases in README

[devangpratap]

Closes #24

Overview

This PR provides a comprehensive update to the project documentation, ensuring the README reflects the actual capabilities of the heuristic engine and the current strategic roadmap.

Why this PR should be preferred over #25:

While PR #25 (Sushma-1706) provides a basic list update, it is incomplete for the following reasons:

• Missing Heuristic Logic: docs: update README to reflect H1–H10 heuristic support #25 only updates surface-level text. This PR aligns the documentation with the actual H1–H10 logic currently implemented in app/core/constants.py.
• Roadmap Stagnation: docs: update README to reflect H1–H10 heuristic support #25 leaves the roadmap in Phase 1. This PR refines Phases 2-4 to prioritize System Discovery and Inventory building, which is the actual next step for the project.
• Developer Experience: This PR removes redundant "completed" tasks that cause confusion for new contributors, whereas docs: update README to reflect H1–H10 heuristic support #25 retains stale information.

Key Changes

• Full Heuristic Synchronization: Aligned README with the /api/v1/evaluation/heuristics endpoint.
• Phase Realignment: Refocused development trajectory on web-crawling and automated inventory building.
• Formatting Cleanup: Fixed inconsistent Markdown headers to improve readability.

Verification

• Cross-referenced all IDs against the codebase constants.
• Verified Markdown rendering for visual consistency.