refactor(database): use a new 'On-Demand' design (#86)

Technical Details: https://blog.mxgame.top/2025/11/22/An-On-Demand-Design-Within-SQLModel/

app/fetcher/beatmap.py

@@ -1,13 +1,40 @@
-from app.database.beatmap import BeatmapResp
+from app.database.beatmap import BeatmapDict, BeatmapModel
 from app.log import fetcher_logger
 
 from ._base import BaseFetcher
 
+from pydantic import TypeAdapter
+
 logger = fetcher_logger("BeatmapFetcher")
+adapter = TypeAdapter(
+    BeatmapModel.generate_typeddict(
+        (
+            "checksum",
+            "accuracy",
+            "ar",
+            "bpm",
+            "convert",
+            "count_circles",
+            "count_sliders",
+            "count_spinners",
+            "cs",
+            "deleted_at",
+            "drain",
+            "hit_length",
+            "is_scoreable",
+            "last_updated",
+            "mode_int",
+            "ranked",
+            "url",
+            "max_combo",
+            "beatmapset",
+        )
+    )
+)
 
 
 class BeatmapFetcher(BaseFetcher):
-    async def get_beatmap(self, beatmap_id: int | None = None, beatmap_checksum: str | None = None) -> BeatmapResp:
+    async def get_beatmap(self, beatmap_id: int | None = None, beatmap_checksum: str | None = None) -> BeatmapDict:
         if beatmap_id:
             params = {"id": beatmap_id}
         elif beatmap_checksum:
@@ -16,7 +43,7 @@ class BeatmapFetcher(BaseFetcher):
             raise ValueError("Either beatmap_id or beatmap_checksum must be provided.")
         logger.opt(colors=True).debug(f"get_beatmap: <y>{params}</y>")
 
-        return BeatmapResp.model_validate(
+        return adapter.validate_python(  # pyright: ignore[reportReturnType]
             await self.request_api(
                 "https://osu.ppy.sh/api/v2/beatmaps/lookup",
                 params=params,