docs: Update documentation to reflect card grid instead of treemap

[raifdmueller]

Context

The visualization changed from treemap to card grid view (ADR-005), but documentation still references the old treemap approach.

Files to Update

High Priority

• docs/PRD.md - Update user stories and functional requirements
  • Line 15: "Interactive treemap" → "Card grid view"
  • Line 86: US-02 about treemap → about card grid
  • Lines 196-200: FR-2.1-2.5 treemap requirements → card grid requirements
  • Line 297: Remove ECharts mention
  • Lines 364, 411, 438-439: Remove treemap implementation tasks

Medium Priority

• docs/specs/01_use_cases.adoc - Update use case diagrams
• docs/specs/02_api_specification.adoc - Update API descriptions
• docs/specs/03_acceptance_criteria.adoc - Update Gherkin scenarios

Low Priority (arc42)

• docs/arc42/chapters/01_introduction_and_goals.adoc
• docs/arc42/chapters/03_context_and_scope.adoc
• docs/arc42/chapters/04_solution_strategy.adoc
• docs/arc42/chapters/05_building_block_view.adoc
• docs/arc42/chapters/06_runtime_view.adoc
• docs/arc42/chapters/08_crosscutting_concepts.adoc
• docs/arc42/chapters/10_quality_requirements.adoc
• docs/arc42/chapters/11_risks_and_technical_debt.adoc
• docs/arc42/chapters/12_glossary.adoc

ADRs

• Mark docs/specs/adrs/adr-003-treemap-library.adoc as Superseded by ADR-005
• Update docs/specs/adrs/adr-001-static-site-generator.adoc (remove ECharts mention)
• Update docs/specs/adrs/adr-002-metadata-storage.adoc if needed

Replacements

Find: treemap, ECharts, Apache ECharts
Replace with: card grid, category sections

Reference

• ✅ ADR-005: Documents the decision and rationale for card grid
• ✅ Implementation: Already done and live

Acceptance Criteria

• No mentions of "treemap" in PRD or specs (except ADR-003/ADR-005)
• All user stories reflect card grid UX
• arc42 architecture matches current implementation