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/shared/errors.ts

@@ -10,6 +10,7 @@ export type ErrorCode =
 	| 'INVALID_PERSON_TYPE'
 	| 'BIRTH_AFTER_DEATH'
 	| 'INVALID_DATE_PRECISION'
+	| 'INVALID_RELATIONSHIP_DATES'
 	| 'INVALID_DATE_RANGE'
 	| 'DOCUMENT_NOT_FOUND'
 	| 'DOCUMENT_NO_FILE'
@@ -106,6 +107,8 @@ export function getErrorMessage(code: ErrorCode | string | undefined): string {
 			return m.error_birth_after_death();
 		case 'INVALID_DATE_PRECISION':
 			return m.error_invalid_date_precision();
+		case 'INVALID_RELATIONSHIP_DATES':
+			return m.error_invalid_relationship_dates();
 		case 'INVALID_DATE_RANGE':
 			return m.error_invalid_date_range();
 		case 'DOCUMENT_NOT_FOUND':

frontend/src/lib/shared/primitives/DateInputWithPrecision.svelte

@@ -0,0 +1,106 @@
+<script lang="ts">
+import { onMount } from 'svelte';
+import DateInput from '$lib/shared/primitives/DateInput.svelte';
+import type { DatePrecision } from '$lib/shared/utils/documentDate';
+
+/**
+ * Compact date + precision field: the {@link DateInput} primitive paired with a
+ * precision <select> offering a caller-chosen subset of precisions. Shared base of
+ * PersonLifeDateField (birth/death) and RelationshipDateField (from/to).
+ *
+ * Distinct from {@link DatePrecisionField} — that one is the full document/timeline
+ * field (all seven precisions, German free-text entry, RANGE end-date disclosure).
+ * This one is the restricted, single-input variant for the person-family forms.
+ *
+ * All copy (legend, precision labels, hint, the select's accessible name) and the
+ * offered precisions are injected by the caller so this stays domain-agnostic.
+ */
+let {
+	name,
+	legend,
+	precisionLabel,
+	hint,
+	precisions,
+	initialIso = '',
+	initialPrecision = null,
+	inputClass = '',
+	selectClass = ''
+}: {
+	name: string;
+	legend: string;
+	precisionLabel: string;
+	hint: string;
+	precisions: { value: DatePrecision; label: string }[];
+	initialIso?: string | null;
+	initialPrecision?: string | null;
+	inputClass?: string;
+	selectClass?: string;
+} = $props();
+
+let iso = $state('');
+let errorMessage = $state<string | null>(null);
+let inputEl = $state<HTMLInputElement | undefined>();
+let precision = $state<DatePrecision>('DAY');
+
+// Seed once at mount so a later load() rerun does not stomp an in-progress edit.
+onMount(() => {
+	if (initialIso) {
+		iso = initialIso;
+	}
+	const offered = precisions.some((p) => p.value === initialPrecision);
+	if (offered) {
+		precision = initialPrecision as DatePrecision;
+	} else if (initialIso) {
+		// A stored non-offered precision (SEASON/RANGE/APPROX) seeds as YEAR so an
+		// untouched save does not silently claim DAY precision for the stored date.
+		precision = 'YEAR';
+	}
+});
+
+// A partial date leaves the hidden ISO empty — block native submission until the
+// date is completed or fully emptied, so a save can never silently clear a date.
+$effect(() => {
+	inputEl?.setCustomValidity(errorMessage ?? '');
+});
+
+const controlCls =
+	'block min-h-[44px] w-full rounded border border-line px-3 py-2 font-serif text-ink focus:outline-none focus-visible:ring-2 focus-visible:ring-focus-ring';
+</script>
+
+<fieldset>
+	<legend class="mb-1 block text-xs font-bold tracking-widest text-ink-3 uppercase">
+		{legend}
+	</legend>
+	<div class="flex flex-col gap-2 sm:flex-row">
+		<div class="flex-1">
+			<DateInput
+				bind:value={iso}
+				bind:errorMessage={errorMessage}
+				bind:inputEl={inputEl}
+				name={name}
+				id={name}
+				placeholder="TT.MM.JJJJ"
+				ariaLabel={legend}
+				ariaDescribedby={errorMessage ? `${name}-error` : undefined}
+				class="{controlCls} {inputClass}"
+			/>
+			{#if errorMessage}
+				<p id="{name}-error" class="mt-1 font-sans text-xs text-red-600">{errorMessage}</p>
+			{/if}
+		</div>
+		<div class="flex-1">
+			<select
+				id="{name}Precision"
+				name="{name}Precision"
+				aria-label="{legend}: {precisionLabel}"
+				bind:value={precision}
+				class="{controlCls} {selectClass}"
+			>
+				{#each precisions as p (p.value)}
+					<option value={p.value}>{p.label}</option>
+				{/each}
+			</select>
+		</div>
+	</div>
+	<p class="mt-1 font-sans text-xs text-ink-3">{hint}</p>
+</fieldset>

frontend/src/lib/shared/utils/documentDate.ts

@@ -66,6 +66,27 @@ export function formatDocumentDate(
 	}
 }
 
+/**
+ * Formats one nullable date at the precision the data claims, delegating all
+ * rendering to {@link formatDocumentDate}. Returns '' for a missing date; a
+ * missing precision falls back to YEAR — pre-precision rows knew only a year,
+ * and a bare year is the only safe rendering without precision metadata.
+ *
+ * This is the shared core of {@link formatLifeDate} (person birth/death) and the
+ * relationship from/to formatter. Range-level glyphs and dashes belong in those
+ * domain wrappers, never here.
+ */
+export function formatDatePart(
+	date: string | null | undefined,
+	precision: DatePrecision | null | undefined,
+	locale?: string
+): string {
+	if (!date) {
+		return '';
+	}
+	return formatDocumentDate(date, precision ?? 'YEAR', null, null, locale);
+}
+
 // ─── precision branches ──────────────────────────────────────────────────────
 
 function longDate(iso: string, locale: string): string {