Add core data model (12 tables) and initial Alembic migration

All core entities from ARCHITECTURE §5: tenancy (User, Tree, TreeMembership), people (Person, Name, Relationship), facts (Event, Place, PlaceName), provenance (Source, Citation), and the append-only AuditEntry. Cross-cutting mixins give every row a UUID key, timestamps, soft delete, and (where tree-owned) a tree_id for uniform tenant isolation.

Modeling choices: parentage as qualified edges (biological/adoptive/step/foster/donor/guardian) so non-traditional families are first-class; events keep both a verbatim date string and a normalized start/end range; closed sets are PG enums while GEDCOM-extensible vocabularies (event/name/source type) stay strings; CHECK constraints enforce single-subject events and single-target citations. Place is tree-scoped in Phase 0 (see ARCHITECTURE note). The migration is verified reversible (upgrade/downgrade drops tables and enum types) and matches the models (alembic check clean); applied on the deploy target. Dockerfile now ships migrations.

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

backend/app/models/enums.py

@@ -0,0 +1,57 @@
+"""Closed-set enumerations that drive logic (authorization, privacy, traversal).
+
+Open-ended, GEDCOM-extensible vocabularies (event type, name type, source type)
+are stored as strings instead, so importing real-world files never fails on an
+unknown tag.
+"""
+
+import enum
+
+
+class TreeVisibility(enum.StrEnum):
+    public = "public"
+    unlisted = "unlisted"
+    private = "private"
+
+
+class MembershipRole(enum.StrEnum):
+    owner = "owner"
+    editor = "editor"
+    viewer = "viewer"
+
+
+class PersonPrivacy(enum.StrEnum):
+    """Per-person override of the tree's visibility (PRD US-041)."""
+
+    inherit = "inherit"
+    private = "private"
+    public = "public"
+
+
+class RelationshipType(enum.StrEnum):
+    parent_child = "parent_child"
+    partnership = "partnership"
+    sibling = "sibling"
+
+
+class ParentChildQualifier(enum.StrEnum):
+    """Qualifies a parent_child edge so adoption/donor/blended families are
+    first-class rather than edge cases (ARCHITECTURE §5)."""
+
+    biological = "biological"
+    adoptive = "adoptive"
+    step = "step"
+    foster = "foster"
+    donor = "donor"
+    guardian = "guardian"
+
+
+class CitationConfidence(enum.StrEnum):
+    high = "high"
+    medium = "medium"
+    low = "low"
+
+
+class AuditActorType(enum.StrEnum):
+    user = "user"
+    assistant = "assistant"