feat: Report builder with modal-based ingredient selection

[anth-volk]

Summary

This PR introduces a completely redesigned Report Builder experience with modal-based workflows for selecting and creating policies, populations, and households. This is a major feature addition that provides users with an intuitive, streamlined interface for configuring policy simulations.

Report builder core

• New ReportBuilderPage with simulation canvas for configuring reports
• Report meta panel for naming reports and viewing configuration status
• Support for single and multi-simulation reports
• Automatic ingredient naming and labeling

Policy selection & creation modal

• PolicyBrowseModal for browsing existing policies or creating new ones
• Policy details drawer showing parameter modifications
• Full policy creation workflow with:
  • Parameter tree navigation with search
  • Value setters for different time modes (default, yearly, date range, multi-year)
  • Historical values chart showing baseline vs reform
  • "Changes for this parameter" list with modification tracking
  • Editable policy naming in header

Population selection & creation modal

• PopulationBrowseModal for geographic and household population selection
• Support for US states, congressional districts, and UK constituencies/local authorities
• Household selection from user's saved households
• Inline household creation modal

Household creation modal

• Integrated household builder within population modal
• Entity-aware variable assignment
• Support for US and UK household structures

Additional improvements

• Geography utilities for US/UK administrative divisions
• Usage tracking infrastructure
• Various visual and UX refinements

⚠️ Draft PR notice

This PR is in draft status. The following still need investigation before merging:

• Test coverage for new components
• Code formatting verification (prettier)
• ESLint / code quality checks
• Manual QA across US and UK flows
• Performance testing with large parameter trees

Test plan

• Create a new report from Report Builder page
• Browse and select existing policies
• Create a new policy with parameter modifications
• Verify parameter changes display correctly in chart and list
• Select geographic populations (nationwide, state, district)
• Create and select household populations
• Complete full report creation flow
• Test both US and UK country contexts

🤖 Generated with Claude Code

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