Add fuzzy name search (pg_trgm) and living-person protection

Fuzzy search: pg_trgm extension + trigram GIN indexes on name parts and a GET /trees/{id}/persons?q= search ranked by trigram similarity (finds Mueller for 'muller'), privacy-filtered. Living-person protection: the privacy engine now derives possibly-living status (explicit flag, else no death fact + birth within ~100y or unknown) and returns 'redacted' for non-members of public/unlisted trees; the service minimises those records ('Living person', no vitals). Members are unaffected. 31 tests pass.

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

backend/app/models/person.py

@@ -7,7 +7,7 @@ aliases) so name changes over time are first-class.
 
 import uuid
 
-from sqlalchemy import Boolean, ForeignKey, Integer, String, Text, text
+from sqlalchemy import Boolean, ForeignKey, Index, Integer, String, Text, text
 from sqlalchemy import Enum as SAEnum
 from sqlalchemy.orm import Mapped, mapped_column
 
@@ -33,6 +33,22 @@ class Person(Base, UUIDPrimaryKey, TenantScoped, Timestamps, SoftDelete):
 
 class Name(Base, UUIDPrimaryKey, TenantScoped, Timestamps, SoftDelete):
     __tablename__ = "names"
+    # Trigram indexes for fuzzy name search (Mueller/Müller/Muller). Requires the
+    # pg_trgm extension (enabled in the accompanying migration).
+    __table_args__ = (
+        Index(
+            "ix_names_given_trgm",
+            "given",
+            postgresql_using="gin",
+            postgresql_ops={"given": "gin_trgm_ops"},
+        ),
+        Index(
+            "ix_names_surname_trgm",
+            "surname",
+            postgresql_using="gin",
+            postgresql_ops={"surname": "gin_trgm_ops"},
+        ),
+    )
 
     person_id: Mapped[uuid.UUID] = mapped_column(
         ForeignKey("persons.id", ondelete="CASCADE"), index=True