Visibility phase 3: redaction-safe public read API + leak test

Adds the anonymous read surface (/api/v1/public) — the privacy-critical core.

- CurrentUserOrNone dependency: optional auth that never 401s (anonymous OK).
- public_view_service: every projection passes through privacy.person_visibility.
  persons redacted (living → "Living person", hidden dropped); relationships
  only when both endpoints non-hidden; events only for FULL-visibility persons
  (partnership events only when both partners full); names only for FULL
  persons. Not-viewable trees raise 404 (not 403) so the surface can't probe
  for private trees. Media deferred (higher-sensitivity; own pass later).
- public router: read-only directory + tree + persons/relationships/events +
  person detail/names/events. Directory lists `public` to all and adds
  `site_members` for authenticated callers; never lists unlisted/private.
- PublicTreeRead omits owner_id.

Tests (ran locally — CI does not run pytest): an anonymous end-to-end leak test
asserting a living person's real name, alias, and birth year appear in NO public
response while the deceased person's data does; plus private=404, unlisted
viewable-by-link-but-unlisted, site_members requires login, and directory
visibility. Full suite: 70 passed. Regenerated openapi.json + TS client.

Note: the AUTHED list endpoints still leak per-person for non-members
(pre-existing) — fixed next, separately.

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

backend/app/api/deps.py

@@ -40,6 +40,18 @@ async def get_current_user(request: Request, session: SessionDep) -> User:
 CurrentUser = Annotated[User, Depends(get_current_user)]
 
 
+async def get_current_user_or_none(request: Request, session: SessionDep) -> User | None:
+    """Optional auth for public read endpoints — never raises. Returns the user
+    when a valid session is present, else None (anonymous viewer)."""
+    raw_token = extract_session_token(request)
+    if raw_token is None:
+        return None
+    return await auth_service.resolve_session_user(session, raw_token=raw_token)
+
+
+CurrentUserOrNone = Annotated[User | None, Depends(get_current_user_or_none)]
+
+
 def get_mailer() -> Mailer:
     settings = get_settings()
     if settings.mailer == "smtp" and settings.smtp_host: