feat(FN-007): implement repository connection API and git operations

- Add GitHubAdapter and GitLabAdapter with URL parsing
- Create provider factory in apps/api/app/git/providers/
- Implement clone, fetch, push in LocalGitOperations
- Add repository_connections router with CRUD and SSH key endpoints
- Create RepositoryConnection schema with validation
- Update models and routers __init__.py for new components
- Add comprehensive tests for git operations

apps/api/app/git/providers/__init__.py

@@ -0,0 +1,17 @@
+from app.git.provider import GitProvider
+from app.git.types import ProviderKind
+
+from .github import GitHubAdapter
+from .gitlab import GitLabAdapter
+
+PROVIDERS: dict[ProviderKind, type[GitProvider]] = {
+    ProviderKind.github: GitHubAdapter,
+    ProviderKind.gitlab: GitLabAdapter,
+}
+
+
+def get_provider(kind: ProviderKind) -> GitProvider:
+    provider_class = PROVIDERS.get(kind)
+    if provider_class is None:
+        raise ValueError(f"Unsupported provider kind: {kind}")
+    return provider_class()