feat(relationship): editable relationships with LocalDate+DatePrecision dates and notes (#841)

Closes #837

Makes `PersonRelationship` fully editable (type, related person, dates, notes), migrates its dates from `Integer fromYear/toYear` to `LocalDate + DatePrecision` (mirroring the #773 person pattern, ADR-039 / V76), activates the previously-dead `notes` column, and gives the Zeitstrahl's derived **Heirat** events full date precision for free.

Both Open Decisions confirmed as adopted: **no `@Version`** (last-write-wins, single-writer archive) and **`DELETE` ownership-mismatch aligned 403 → 404** (anti-enumeration, matching the new `PUT`).

## What's in it
- **V78** migrates `person_relationships.from_year/to_year` → `from_date`/`to_date` + NOT-NULL `*_date_precision` (default `UNKNOWN`); pre-check abort on corrupt years, `YYYY-01-01`/`YEAR` backfill, 5 named CHECK constraints, year columns dropped.
- **`PUT /api/persons/{id}/relationships/{relId}`** (`@RequirePermission(WRITE_ALL)`) re-runs every create invariant (self / coherence / order / reverse-PARENT_OF / duplicate) and re-flags family membership; orientation preserved per viewpoint.
- New `ErrorCode.INVALID_RELATIONSHIP_DATES` registered in all four sites (§3.6).
- `TimelineEventService` sources the derived marriage date from `SPOUSE_OF.fromDate` + precision.
- Frontend: `RelationshipDateField` (DAY/MONTH/YEAR), upsert-capable `AddRelationshipForm` (pre-fill + notes + in-flight submit lock), `RelationshipChip` Edit affordance, `updateRelationship` server action, read-view date range + notes, `formatRelationshipDateRange` helper. `api.ts` regenerated.
- Docs: ADR-044, db-orm/db-relationships diagrams, DEPLOYMENT §5 deploy note, RTM REQ-001…REQ-019.

## Requirements
All 19 EARS requirements implemented red/green and marked `Done` in `.specify/rtm.md`.

## Test plan
- **Backend** (targeted, green): `RelationshipMigrationTest` (Testcontainers pg16, 8), `RelationshipServiceTest` (22), `RelationshipControllerTest` (15), `RelationshipServiceIntegrationTest` (real DB, 10), `DerivedEventsAssemblyTest` (17), `ArchitectureTest` (14); `clean package` builds.
- **Frontend** (green): `relationshipDates.spec.ts`, `AddRelationshipForm.svelte.spec.ts`, `RelationshipChip.svelte.spec.ts`, `PersonRelationshipsCard.svelte.test.ts`, `page.server.spec.ts`, `messages.spec.ts`. `npm run check` = 798 (below the ~834 baseline); `npm run lint` clean.

## Notes for reviewers
- **Spec deviation:** the edit form was built by making `AddRelationshipForm` upsert-capable rather than a duplicate `EditRelationshipForm` (DRY); RTM rows reference `AddRelationshipForm.svelte.spec.ts`.
- `api.ts` regenerated from the live spec; only relationship-relevant hunks remain (one springdoc `PageableObject` field-reorder pruned).
- **Deploy:** V78 is one-way and not rolling-deploy-safe — stop old JAR → start new JAR (Flyway runs first); targeted `pg_restore -t person_relationships` for rollback. No maintenance window.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Marcel <marcel@familienarchiv>
Reviewed-on: #841

frontend/src/lib/person/genealogy/StammbaumCard.svelte.test.ts

@@ -111,17 +111,21 @@ describe('StammbaumCard', () => {
 		expect(items.length).toBeGreaterThanOrEqual(2);
 	});
 
-	it('renders the year range "from–to" for a relationship with both years', async () => {
+	it('renders the date range "from – to" for a relationship with both dates', async () => {
 		render(StammbaumCard, {
 			props: baseProps({
 				relationships: [
 					{
 						id: 'r-1',
+						personId: 'p-1',
+						relatedPersonId: 'p-x',
+						personDisplayName: 'Anna',
+						relatedPersonDisplayName: 'Xavier',
 						relationType: 'COLLEAGUE',
-						fromYear: 1940,
-						toYear: 1945,
-						personA: { id: 'p-1', displayName: 'Anna' },
-						personB: { id: 'p-x', displayName: 'Xavier' }
+						fromDate: '1940-01-01',
+						fromDatePrecision: 'YEAR',
+						toDate: '1945-01-01',
+						toDatePrecision: 'YEAR'
 					}
 				]
 			})
@@ -131,23 +135,27 @@ describe('StammbaumCard', () => {
 		expect(document.body.textContent).toContain('1945');
 	});
 
-	it('renders only "fromYear" for a relationship with no end year', async () => {
+	it('renders only the start date for a relationship with no end date', async () => {
 		render(StammbaumCard, {
 			props: baseProps({
 				relationships: [
 					{
 						id: 'r-2',
+						personId: 'p-1',
+						relatedPersonId: 'p-y',
+						personDisplayName: 'Anna',
+						relatedPersonDisplayName: 'Yvonne',
 						relationType: 'NEIGHBOR',
-						fromYear: 1935,
-						personA: { id: 'p-1', displayName: 'Anna' },
-						personB: { id: 'p-y', displayName: 'Yvonne' }
+						fromDate: '1935-01-01',
+						fromDatePrecision: 'YEAR',
+						toDatePrecision: 'UNKNOWN'
 					}
 				]
 			})
 		});
 
 		expect(document.body.textContent).toContain('1935');
-		expect(document.body.textContent).not.toContain('1935–');
+		expect(document.body.textContent).not.toContain('1935 –');
 	});
 
 	it('renders the inferred-relationships disclosure when topDerived has items', async () => {