feat(demo-admin-dashboard): Campaign draft snapshot support and restore confirmation

[Agbasimere]

Labels

demo-admin-dashboard, demo-data, Campaign

Closes #277

Description

This PR implements Campaign Draft Snapshot Support for the Demo Admin Dashboard initiative (Campaign issue 26 of 50). It allows maintainers to save snapshots of the currently built draft dataset, list existing snapshots, inspect detailed metadata (target audience, timestamp, tags, draft list), and restore previous campaign draft states with a restore confirmation prompt.

Scope & Constraints

• All changes are strictly confined to src/features/demo-admin-dashboard/.
• No files outside src/features/demo-admin-dashboard/ were modified.
• Resolved pre-existing merge conflict markers in src/features/demo-admin-dashboard/index.ts and src/features/demo-admin-dashboard/README.md.
• Cleared pre-existing TypeScript compilation issues in src/features/demo-admin-dashboard/DemoDashboard.tsx by declaring the missing DemoUser and DemoItem types in types.ts.

Deliverables & Key Changes

1. Types: Created types/campaignSnapshot.ts containing the CampaignSnapshot schema.
2. Fixtures: Created fixtures/campaignSnapshotFixtures.ts containing three public-safe, deterministic, and fake default campaign snapshots (Welcome Series, Security Onboarding, Monthly Newsletter).
3. Persistence: Updated persistence/localStorageAdapter.ts with convenience get/save/clear helpers for the active draft dataset and campaign snapshots (falling back to preloaded defaults when empty).
4. UI Components:
   • Built components/CampaignSnapshots.tsx representing the new Campaigns dashboard section. It allows saving, viewing metadata, deleting, and restoring snapshots with a confirmation step detailing active vs target draft counts.
   • Lifted dataset state in DemoAdminDashboard.tsx to keep the Templates tab and Campaigns tab in sync.
5. Documentation: Updated README.md to resolve conflicts and document the new Campaign Snapshots feature.
6. Tests:
   • Added unit tests in __tests__/campaignSnapshots.test.ts to test default fallback snapshots, custom saving, retrieval, deletion, and schema validations.
   • Added unit tests in __tests__/localStorageAdapter.test.ts to check storage adapter get/save operations.
   • All 37 feature tests pass successfully.

Testing Checklist

• Unit tests pass: npx vitest run src/features/demo-admin-dashboard/__tests__/
• Codebase formatting matches Prettier: npx prettier --check src/features/demo-admin-dashboard/
• Compilation completes without issues: npm run build

[kryputh]

Fix conflict

[Agbasimere]

@kryputh Resolved.