Add update (CRUD) for events and people; record the full-CRUD invariant

Events and people are now editable, not write-once: PATCH /events/{id} (type, structured date, place, notes) and PATCH /persons/{id} (vitals, privacy, and the primary name's given/surname). CLAUDE.md gains rule #8: every stored object must support full CRUD in API and UI — historical research is constant correction. Tests cover both updates.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Justin Paul <justin@jpaul.me>

CLAUDE.md

@@ -19,6 +19,7 @@ These are product invariants, not preferences. Do not violate them, and flag any
 5. **Sources are first-class.** Don't model citations as free-text afterthoughts. A `Source` is a reusable entity; a `Citation` links it to a specific fact.
 6. **Only legal data sources.** Ship scrapers/connectors only for permissible sources (FamilySearch API, Find A Grave, WikiTree, BLM/GLO, USGS, public-domain newspapers, public county records). Never add connectors for paywalled/terms-prohibited sites (Ancestry, MyHeritage, 23andMe).
 7. **Everything is configurable via environment.** Auth, mail, object storage, database, model providers, scrapers — all twelve-factor. No hard-coded endpoints or keys.
+8. **Full CRUD on every object.** Every stored entity (person, name, event, relationship, source, citation, media, tree, …) must support create, read, **update**, and delete — in the API *and* the UI. Historical research is constant correction and new information, so nothing is write-once. Any new feature or data type ships with all four operations; an entity you can create but not edit is a bug.
 
 ## Tech stack