Tree Cleanup tool: bulk fixes with preview → approve

A new per-tree Cleanup page (and cleanup_service + endpoints), each fix
preview-first per the propose-then-approve rule:

- Mark deceased by birth year: lists people born ≤ a cutoff (default 1930) not
  already deceased; apply sets is_living=false for the ones you keep checked.
- Set sex from a source GEDCOM: upload the source .ged (it carries SEX); matches
  by name and proposes sex only where it's missing — far more accurate than
  guessing from first names. Review, then apply.
- Names that look broken: flags date-in-surname / date-in-given / no-surname /
  packed given names, with inline editable given+surname; fix the checked ones.

No migration (uses existing columns). 55 backend tests pass (preview+apply for
all three); frontend builds.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/app/api/v1/__init__.py

@@ -5,6 +5,7 @@ from fastapi import APIRouter
 from app.api.v1 import (
     auth,
     citations,
+    cleanup,
     events,
     gedcom,
     media,
@@ -28,3 +29,4 @@ api_router.include_router(sources.router)
 api_router.include_router(citations.router)
 api_router.include_router(media.router)
 api_router.include_router(gedcom.router)
+api_router.include_router(cleanup.router)