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

docs/adr/044-relationship-dates-localdate-precision.md

@@ -0,0 +1,91 @@
+# ADR-044 — Relationship dates become LocalDate + DatePrecision; relationships become editable
+
+**Status:** Accepted
+**Date:** 2026-06-14
+**Issue:** #837 (Zeitstrahl milestone; deferred follow-up to #773 / ADR-039)
+
+## Context
+
+`PersonRelationship` stored its span as `Integer fromYear`/`toYear`. A wedding could
+never be more precise than `1923`, while `Person` (ADR-039), `Document`, and
+`TimelineEvent` already carry full `DatePrecision`. Relationships also supported only
+create + delete: fixing a wrong type, a wrong person, or adding a date learned later
+meant deleting and re-creating the edge — losing `createdAt`. A `notes` column existed
+that no form set and nothing displayed.
+
+V78 replaces the two integer columns with `from_date`/`to_date` (`DATE`, nullable) plus
+`from_date_precision`/`to_date_precision` (`VARCHAR(16) NOT NULL DEFAULT 'UNKNOWN'`),
+backfilling existing years as `YYYY-01-01` at `YEAR` precision — exactly the V76 / ADR-039
+pattern applied to the relationship edge. A new `PUT /api/persons/{id}/relationships/{relId}`
+makes relationships editable, and `notes` is activated end to end.
+
+## Decisions
+
+### 1. Mirror ADR-039 verbatim for the relationship edge
+
+`DatePrecision` is imported cross-domain from `document/` (ADR-039 §1 — value-type
+sharing, not a layering breach). The precision columns are NOT NULL default `UNKNOWN`,
+guarded by five named CHECK constraints (`chk_relationship_from_coherence`,
+`chk_relationship_to_coherence`, `chk_relationship_date_order`,
+`chk_relationship_{from,to}_precision_values`). `RelationshipService.validateRelationshipDates`
+enforces the same rules first, so the user gets a structured 400
+(`INVALID_DATE_PRECISION` for coherence, the new `INVALID_RELATIONSHIP_DATES` for a
+`toDate < fromDate` order violation) instead of a constraint-violation 500. The form
+offers only **DAY / MONTH / YEAR**; storage still accepts all seven values, and a
+stored non-offered precision seeds the edit select as `YEAR` (ADR-039 §2).
+
+### 2. Update re-runs every create invariant
+
+An edit can violate the same invariants as a create, so `updateRelationship` re-runs
+all of them: self-relation (`VALIDATION_ERROR`), date coherence + order, reverse
+`PARENT_OF` (`CIRCULAR_RELATIONSHIP`), and the `(person, relatedPerson, type)` unique
+constraint via `saveAndFlush` (`DUPLICATE_RELATIONSHIP`). Editing into a family type
+flags both endpoints as family members (additive; never auto-unflags). The directed
+orientation is preserved per viewpoint — whichever endpoint `{personId}` already holds
+on the row stays put — so a `PARENT_OF` edge remains parent→child whether edited from
+either person's page.
+
+### 3. No optimistic locking (`@Version`)
+
+`PersonRelationship` gains no `@Version`; the edit is last-write-wins, matching the
+person edit form. This is a single-writer family archive, and it avoids the managed-
+`setVersion` pitfall (a `setVersion` on a managed entity is silently ignored by
+Hibernate — see the integration-test note in #496-era work). If concurrent curation
+ever becomes real, add `@Version` plus an explicit client-version compare then.
+
+### 4. IDOR / anti-enumeration: ownership mismatch is 404, for PUT **and** DELETE
+
+A `{relId}` that does not belong to `{personId}` returns 404 `RELATIONSHIP_NOT_FOUND`
+(a shared `loadOwnedRelationship` helper), so a curator cannot probe relationship ids
+belonging to people they cannot see. This **aligns `deleteRelationship`** from its
+former 403 to 404 in the same change, so the two mutating endpoints behave identically
+on the same mismatch.
+
+### 5. Derived marriage events gain precision for free
+
+`TimelineEventService.buildMarriageEvents` now sources the Heirat date from the
+`SPOUSE_OF` row's `from_date` + `from_date_precision` (previously
+`LocalDate.of(fromYear, 1, 1)` at hard-coded `YEAR`). A DAY-precision wedding now
+surfaces the exact day on the Zeitstrahl. `RelationshipInferenceService` is unchanged
+— it is time-ignorant and never read the year fields.
+
+### 6. `relationshipDates.ts` lives in `$lib/person/`, no new boundary
+
+`formatRelationshipDateRange` mirrors `personLifeDates.ts` and delegates entirely to the
+already-tested `formatDocumentDate` (zero new precision logic). It sits in `$lib/person/`
+next to `personLifeDates.ts`; its only cross-domain import is `formatDocumentDate` from
+`$lib/shared/utils/`, which the existing `person → shared` rule in `eslint.config.js`
+already permits — **no new eslint boundary rule is added**.
+
+## Consequences
+
+- V78 is one-way (columns dropped) and is **not** rolling-deploy-safe — the running JAR
+  maps `from_year` until redeploy. Deploy order: **stop old JAR → run Flyway V78 →
+  start new JAR**. Rollback = targeted `pg_restore -t person_relationships` from the
+  pre-deploy dump (see `docs/DEPLOYMENT.md` §8). No maintenance window needed
+  (single-writer archive).
+- Relationships are fully editable (type, related person, dates, notes) and the read
+  view shows the date range + notes.
+- `RelationshipDTO` drops `fromYear`/`toYear` for `fromDate`/`fromDatePrecision`/
+  `toDate`/`toDatePrecision`; the `personBirthYear`/`relatedPersonBirthYear` derived
+  fields are unaffected (ADR-039 §3).