feat(dm-dashboard): Wave 7 — FREE→PRO data import flow (Task 22)

Adds an opt-in modal that prompts a PRO user with local data to migrate
their localStorage notes and sessionStorage initiative into the cloud.

- src/lib/client/import.ts: pure helpers (hasLocalData, shouldShowImport)
- src/components/dm/ImportModal.astro: modal UI + import orchestration
  with conflict handling for existing "DM Notes" record
- src/i18n/dm-translations.ts: 14 new keys for the import flow
- Wired into both EN and RU dm/index.astro
- tests/import-flow.test.ts: 18 unit tests on the helpers

Local storage is preserved as backup; only a "dm-import-asked" flag is
set after the user makes a decision (import or skip).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.sisyphus/plans/dm-dashboard-ai.md

@@ -1599,7 +1599,7 @@ Max Concurrent: 6 (Wave 6)
   - Message: `feat(pro): add initiative DB persistence for PRO users`
   - Files: `src/components/dm/InitiativeTracker.astro`, `src/lib/client/initiative.ts`
 
-- [ ] **22. Add FREE → PRO Data Import Flow**
+- [x] **22. Add FREE → PRO Data Import Flow**
 
   **What to do**:
   - Create import modal/dialog: when FREE user subscribes to PRO (tier changes to 'pro'), show "Import existing data?" prompt.