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/base.py

@@ -0,0 +1,20 @@
+"""Declarative base with a stable constraint-naming convention.
+
+A fixed naming convention is important so Alembic generates deterministic,
+human-readable names for indexes/constraints across migrations.
+"""
+
+from sqlalchemy import MetaData
+from sqlalchemy.orm import DeclarativeBase
+
+NAMING_CONVENTION = {
+    "ix": "ix_%(column_0_label)s",
+    "uq": "uq_%(table_name)s_%(column_0_name)s",
+    "ck": "ck_%(table_name)s_%(constraint_name)s",
+    "fk": "fk_%(table_name)s_%(column_0_name)s_%(referred_table_name)s",
+    "pk": "pk_%(table_name)s",
+}
+
+
+class Base(DeclarativeBase):
+    metadata = MetaData(naming_convention=NAMING_CONVENTION)