Persist skip_on_away on quest definitions

Add a skip_on_away flag to quest_definitions (migration 8, additive
column defaulting to 1 so existing rows keep today's behaviour). The
admin create/edit routes accept it as an optional boolean (create
defaults true, an omitted edit field keeps the stored value) and the
definition payload returns it. Materialisation generates instances on
absent dates when the flag is false.

Task: ded75ab8-0219-4d52-aefa-82c09e0b5e6b

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

custom_components/nestquest/core/migrations.py

@@ -30,8 +30,9 @@ widened (definition_id, child_id, due_date, window) key, and migration
 6 rebuilds ``completion_events`` with the D-008 ``actor_child_id``
 column.  Migration 7 adds the generic ``nestquest_meta_state``
 key/value table for integration-owned bookkeeping (Feature 11's
-missed-sweep watermark).  Each callable migration runs inside its own
-transaction
+missed-sweep watermark).  Migration 8 adds the ``skip_on_away``
+column to ``quest_definitions`` (Feature 22), defaulting to 1.  Each
+callable migration runs inside its own transaction
 together with its version stamp, so a crash mid-step rolls the
 statements and the stamp back together.
 
@@ -400,6 +401,28 @@ async def _add_actor_child_id(
         await database.execute("PRAGMA foreign_keys = ON")
 
 
+async def _add_skip_on_away(
+    database: NestQuestDatabase, target_version: int
+) -> None:
+    """Add the ``skip_on_away`` column to ``quest_definitions``.
+
+    Strictly additive: ``ALTER TABLE ... ADD COLUMN`` with a NOT NULL
+    DEFAULT 1, so existing rows read as 1 (skip absent dates — the
+    behaviour before the flag existed).  Fresh databases already carry
+    the column from the canonical DDL, so the ALTER is guarded and the
+    step only stamps there.
+    """
+    async with database.transaction():
+        if not await _table_has_column(
+            database, "quest_definitions", "skip_on_away"
+        ):
+            await database.execute(
+                "ALTER TABLE quest_definitions ADD COLUMN "
+                "skip_on_away INTEGER NOT NULL DEFAULT 1"
+            )
+        await stamp_schema_version(database, target_version)
+
+
 #: The ordered migration list.  Append-only: never edit an applied
 #: entry, add the next one instead.  (Migration 1's content was
 #: rewritten pre-release per D-007 — no version 1 database shipped.)
@@ -423,6 +446,10 @@ MIGRATIONS: Sequence[MigrationStep] = [
     # fresh databases (which already made it in migration 1) and
     # pre-v7 databases.  Strictly additive; no existing table changes.
     list(SCHEMA_V7_META_STATE_DDL),
+    # Migration 8 (Feature 22): the skip_on_away flag on
+    # quest_definitions — an additive column defaulting to 1, so every
+    # pre-existing definition keeps today's skip-when-absent behaviour.
+    _add_skip_on_away,
 ]