feat(translate): move write settings to Target Config tab + fix datasource name lookup

Fixes:
- Move batch size, upsert strategy, include source reference
  from Config tab to Target Config tab (Write Settings section)
- Fix 'Dataset #26' fallback — look up real datasource name
  via API when source_table is not saved in job data
- Persist include_source_reference in save payload and
  restore from job data on load (was a pre-existing gap)

QA review fixes:
- Update @BRIEF contracts for both tabs
- Fix import indentation in +page.svelte

Other: help tooltips on translate pages, flow hint on list page,
git migration manager components, dashboard hub pages,
migration settings pages

.opencode/agents/fullstack-coder.md

@@ -76,6 +76,8 @@ You own:
 ## API Contract Conventions (ss-tools)
 - Backend: Pydantic models in `backend/src/schemas/`
 - Frontend: TypeScript types in `frontend/src/types/`
+- **Frontend DTOs MUST match backend Pydantic schemas** — agent must verify type alignment across the stack boundary. Model `.svelte.ts` files use typed atoms conforming to frontend DTOs.
+- `any` is forbidden at the API boundary — use `unknown` with runtime validation/narrowing.
 - URL prefix: `/api/` for REST, `/ws/` for WebSocket
 - Response envelope: `{ status, data, error, meta }` 
 - Error codes: Consistent across backend and frontend