feat(timeline): add EventForm curator create/edit form

One component for both routes: /new renders it empty, /[id]/edit seeds it from a
TimelineEventView. Composes EventTypeSelect, the shared DatePrecisionField, a
plain-textarea description, PersonMultiSelect and DocumentMultiSelect (personIds
/documentIds hidden inputs). lg:grid-cols-[2fr_1fr] collapsing to one column
below lg, sticky save bar, beforeNavigate unsaved-changes guard, submitting flag
via use:enhance (disabled submit), and a delete form gated by getConfirmService()
read lazily so the component mounts cleanly in isolation. Title/description/chip
labels render via default {...} escaping (CWE-79). Seeded DocumentRefs degrade
gracefully to DocumentOption (no precision fields). Pickers gain an inputId prop
so <label for> associates the control; eslint boundaries now lets timeline import
person+document (mirrors the geschichte editor). 6/6 component specs green.

Refs #781
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/eslint.config.js

@@ -199,7 +199,12 @@ export default defineConfig(
 						{ from: { type: 'user' }, allow: { to: { type: ['shared'] } } },
 						{ from: { type: 'notification' }, allow: { to: { type: ['shared'] } } },
 						{ from: { type: 'conversation' }, allow: { to: { type: ['shared'] } } },
-						{ from: { type: 'timeline' }, allow: { to: { type: ['shared'] } } },
+						// Timeline curator event editor selects persons and documents by
+						// design (mirrors the geschichte editor) — #781.
+						{
+							from: { type: 'timeline' },
+							allow: { to: { type: ['shared', 'person', 'document'] } }
+						},
 						{ from: { type: 'shared' }, allow: { to: { type: ['shared'] } } },
 						{
 							from: { type: 'routes' },