remove github service, update routes, schema and resolvers to match n…

[neSpecc]

This PR improves GitHub integration by moving to workspace-level installations and supporting multiple GitHub App installations per workspace, as well as multiple GitHub OAuth authorizations per user.

Key changes

GitHub integration

• Support for multiple GitHub App installations per workspace (new WorkspaceModel methods and GraphQL updates).
• Refactored installation state store (Redis) to include workspaceId, projectId, userId, and timestamp for better flow tracking and CSRF protection.
• Removed legacy project-level installation logic.

User model

• Support for multiple GitHub OAuth authorizations per user (upsert, lookup, active retrieval).

GraphQL

• Added types for workspace integrations and GitHub installations.
• Extended TaskManagerGitHubRepository with repoLanguage.

Dependencies

• Migrated to @hawk.so/github-sdk and updated @hawk.so/types.
• Removed legacy GitHub service usage.