feat(client-verification): add client verification (#104)

New configurations:

- `CHECK_CLIENT_VERSION` enables the check (default=True)
- `CLIENT_VERSION_URLS` contains a chain of valid client hashes. [osu!](https://osu.ppy.sh/home/download) and [osu! GU](https://github.com/GooGuTeam/osu/releases) are valid by default. View [g0v0-client-versions](https://github.com/GooGuTeam/g0v0-client-versions) to learn how to support your own client.

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

app/models/version.py

@@ -0,0 +1,27 @@
+from typing import NamedTuple, TypedDict
+
+
+class VersionInfo(TypedDict):
+    version: str
+    release_date: str
+    hashes: dict[str, str]
+
+
+class VersionList(TypedDict):
+    name: str
+    versions: list[VersionInfo]
+
+
+class VersionCheckResult(NamedTuple):
+    is_valid: bool
+    client_name: str = ""
+    version: str = ""
+    os: str = ""
+
+    def __bool__(self) -> bool:
+        return self.is_valid
+
+    def __str__(self) -> str:
+        if self.is_valid:
+            return f"{self.client_name} {self.version} ({self.os})"
+        return "Invalid Client Version"