Replace presence schedules with multiple presence patterns per child (schema 9)

A child now carries zero or more home/away presence patterns instead of
at most one schedule. Migration 9 creates presence_patterns, copies every
presence_schedules row across as a 'home' pattern named "Home schedule"
(cycle, anchor and pattern verbatim), and drops the old table in one
transaction. Migration 1 keeps creating the retired table from a frozen
copy of its DDL; schema.py no longer declares it.

PresenceEngine resolves override -> any covering away pattern (absent)
-> any covering home pattern (present) -> otherwise absent when the child
has a home pattern, else present. The home-pattern default keeps every
migrated child's presence unchanged.

The admin plane's one-per-child presence-schedule routes are replaced by
pattern CRUD: GET/POST /children/{child_id}/presence-patterns and
PATCH/DELETE /presence-patterns/{pattern_id}.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_api_admin_presence_consequence.py

@@ -124,18 +124,20 @@ async def _create_daily_definition(
     return created.json()["id"]
 
 
-async def _set_custody_schedule(client: object, child_id: int) -> None:
-    """Anchor the two-week custody cycle on today (week 0 starts today)."""
-    response = await client.put(
-        f"/api/v1/admin/children/{child_id}/presence-schedule",
+async def _set_custody_pattern(client: object, child_id: int) -> None:
+    """Add the two-week custody home pattern anchored on today (week 0)."""
+    response = await client.post(
+        f"/api/v1/admin/children/{child_id}/presence-patterns",
         json={
+            "name": "Custody",
+            "kind": "home",
             "cycle_length_weeks": 2,
             "anchor_date": _day(0),
             "pattern": CUSTODY_PATTERN,
         },
         headers=_admin_headers(),
     )
-    assert response.status_code == 200
+    assert response.status_code == 201
 
 
 async def _materialize_horizon(database: object) -> None:
@@ -210,7 +212,7 @@ async def custody(temp_db_path: str) -> SimpleNamespace:
             client, child_id, "Feed the fish", ["afternoon"],
             skip_on_away=False,
         )
-        await _set_custody_schedule(client, child_id)
+        await _set_custody_pattern(client, child_id)
         await _materialize_horizon(database)
         yield SimpleNamespace(
             client=client,
@@ -290,7 +292,7 @@ async def test_skip_on_away_false_definition_contributes_nothing(
             client, child_id, "Feed the fish", ["morning"],
             skip_on_away=False,
         )
-        await _set_custody_schedule(client, child_id)
+        await _set_custody_pattern(client, child_id)
         await _materialize_horizon(database)
         assert await _consequence(client, _body(child_id, 0, 14)) == 0