Add the nightly missed-quest sweep

Fires one nestquest_quest_missed event per past-due open instance at
the configured rollover time and at startup, watermark-guarded in the
new nestquest_meta_state table (migration 7, strictly additive).
Read-only over the domain tables; never reports an instance that was
ever completed.

custom_components/nestquest/dao_meta.py

@@ -0,0 +1,44 @@
+"""Typed DAO for the integration-owned ``nestquest_meta_state`` table.
+
+Generic persistent key/value bookkeeping that belongs to the
+integration itself rather than any domain table — currently the
+Feature 11 missed-sweep watermark.  Values are plain strings; callers
+interpret them.  All SQL for this table lives here per the feature
+guardrails, and every method runs through
+:class:`~.db.NestQuestDatabase` so nothing blocks the event loop.
+"""
+from __future__ import annotations
+
+from .dao_children import _connection_lock
+from .db import NestQuestDatabase
+
+_TABLE = "nestquest_meta_state"
+
+
+class MetaStateDao:
+    """Typed async access to the ``nestquest_meta_state`` table."""
+
+    def __init__(self, database: NestQuestDatabase) -> None:
+        self._database = database
+
+    async def get(self, key: str) -> str | None:
+        """Return the stored value for ``key``, or None when absent."""
+        row = await self._database.fetch_one(
+            f"SELECT value FROM {_TABLE} WHERE key = ?", (key,)
+        )
+        return row[0] if row is not None else None
+
+    async def set(self, key: str, value: str) -> None:
+        """Upsert one key/value row atomically.
+
+        The write runs inside one transaction under the shared
+        connection lock, so a racing reader either sees the old value
+        or the fully-written new one, never a half-applied state.
+        """
+        async with _connection_lock(self._database):
+            async with self._database.transaction():
+                await self._database.execute(
+                    f"INSERT INTO {_TABLE} (key, value) VALUES (?, ?) "
+                    "ON CONFLICT (key) DO UPDATE SET value = excluded.value",
+                    (key, value),
+                )