Quest windows via quest_definition_windows (D-008)

Per IMPLEMENTATION-ORDER.md 1.4: a quest_definition_windows table
(definition_id, window, due_time) declares which day windows a
definition spans, one row per definition+window via the composite
primary key; window is CHECK-constrained to morning/afternoon/evening.

- const.py: WINDOW_MORNING/AFTERNOON/EVENING, QUEST_WINDOWS canonical
  order, WINDOW_CLOCK_RANGES with the documented boundaries and the
  boundary-to-later-window rule documented for Feature 07.
- schema.py: windows DDL joins SCHEMA_V1_STATEMENTS; due_time is
  caller-validated strict HH:MM (DAO layer), matching the date policy.
- migrations.py: migration 4 is a plain CREATE IF NOT EXISTS statement
  list (no rebuild needed for a new table).
- dao_rules.py: QuestDefinitionsDao gains upsert_window (idempotent
  per window, due_time refresh in place), list_windows (const order),
  remove_window; _validate_time/_validate_window helpers.
- tests: windows DDL shape/constraints (CHECK matrix, duplicate,
  unknown definition), DAO round-trips, const range shapes; leak
  guards extended to the new table.

custom_components/nestquest/migrations.py

@@ -73,6 +73,7 @@ from .schema import (
     QUEST_DEFINITIONS_TABLE_SQL,
     SCHEMA_V1_STATEMENTS,
     SCHEMA_V1_QUEST_DEFINITION_ASSIGNEES_DDL,
+    SCHEMA_V1_QUEST_DEFINITION_WINDOWS_DDL,
 )
 
 LOGGER = logging.getLogger(__name__)
@@ -256,6 +257,10 @@ MIGRATIONS: Sequence[MigrationStep] = [
     MIGRATION_1_V1_DDL,
     _rename_legacy_task_tables,
     _add_definition_assignees,
+    # Migration 4 (D-008): the windows table is a plain new table — a
+    # CREATE IF NOT EXISTS suffices for both fresh databases (which
+    # already made it in migration 1) and pre-window databases.
+    list(SCHEMA_V1_QUEST_DEFINITION_WINDOWS_DDL),
 ]