Add events and relationships API (Phase 1: flesh out the graph)

Events (create/list-per-person/soft-delete) and relationships (create/list-per-person/soft-delete) through the layered stack: editor-gated writes, privacy-engine reads, audit on every change. Events carry exactly one subject (person XOR partnership); relationships are typed qualified edges (parent_child gets a biological/adoptive/step/foster/donor/guardian qualifier). Adds a single-person GET. 18 tests pass.

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

backend/app/schemas/relationship.py

@@ -0,0 +1,28 @@
+import uuid
+from datetime import datetime
+
+from pydantic import BaseModel, ConfigDict
+
+from app.models.enums import ParentChildQualifier, RelationshipType
+
+
+class RelationshipCreate(BaseModel):
+    type: RelationshipType
+    person_from_id: uuid.UUID
+    person_to_id: uuid.UUID
+    # Only meaningful for parent_child edges (from = parent, to = child).
+    qualifier: ParentChildQualifier | None = None
+    notes: str | None = None
+
+
+class RelationshipRead(BaseModel):
+    model_config = ConfigDict(from_attributes=True)
+
+    id: uuid.UUID
+    tree_id: uuid.UUID
+    type: RelationshipType
+    person_from_id: uuid.UUID
+    person_to_id: uuid.UUID
+    qualifier: ParentChildQualifier | None
+    notes: str | None
+    created_at: datetime