refactor(proxy): move proxy logic to services.mitmproxy and update Docker service model

- Rename DockerService to DockerContainer and add folder attribute
- Move proxy-related modules (models, validator) to services.mitmproxy
- Update imports and references to new module locations
- Refactor Docker utilities to use DockerContainer and improve service discovery
- Add manager.py with create_proxy utility stub
- Initialize discovered Docker services at app startup and warn if none found

app/integrations/docker/models.py

@@ -1,6 +1,8 @@
+from pathlib import Path
 from typing import TypedDict
 
 
-class DockerService(TypedDict):
+class DockerContainer(TypedDict):
     name: str
     ports: list[int]
+    folder: Path