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/event.py

@@ -0,0 +1,39 @@
+import uuid
+from datetime import date, datetime
+
+from pydantic import BaseModel, ConfigDict
+
+
+class EventCreate(BaseModel):
+    event_type: str
+    # Exactly one subject: a person or a partnership (relationship).
+    person_id: uuid.UUID | None = None
+    relationship_id: uuid.UUID | None = None
+    place_id: uuid.UUID | None = None
+    # Verbatim date string (e.g. "ABT 1850") and/or a normalized range.
+    date_value: str | None = None
+    date_start: date | None = None
+    date_end: date | None = None
+    date_precision: str | None = None
+    calendar: str = "gregorian"
+    detail: str | None = None
+    notes: str | None = None
+
+
+class EventRead(BaseModel):
+    model_config = ConfigDict(from_attributes=True)
+
+    id: uuid.UUID
+    tree_id: uuid.UUID
+    event_type: str
+    person_id: uuid.UUID | None
+    relationship_id: uuid.UUID | None
+    place_id: uuid.UUID | None
+    date_value: str | None
+    date_start: date | None
+    date_end: date | None
+    date_precision: str | None
+    calendar: str
+    detail: str | None
+    notes: str | None
+    created_at: datetime