Feature Request: Generic Git server integration (GitLab, Gitea, Forgejo, etc.)

### Summary

Add support for integrating with **any Git server** that supports Git over HTTP(S) and basic REST/GraphQL APIs. This should include popular self-hosted solutions like **GitLab**, **Gitea**, **Forgejo**, and others.

### Motivation

Many teams use self-hosted Git servers for privacy, compliance, or cost reasons. A flexible integration would make Huly viable for those environments without relying solely on GitHub.

### Proposed Features

- **Server configuration**:
- Git server base URL
- Personal Access Token (PAT) or OAuth2 token
- Optional: self-signed certificate handling / custom CA
- **Auto-detection**:
- Detect server type (GitLab, Gitea, Forgejo, etc.) and adapt API calls accordingly.
- **Repository linking**:
- Map repositories to Huly projects.
- Display commits, branches, and merge requests inside Huly UI.
- **Webhook support**:
- Receive push, PR, and issue events via webhooks.
- Allow linking commits to tasks via commit messages (e.g., `Fixes TASK-123`).
- **Permissions**:
- Respect repository visibility and user permissions.

### Acceptance Criteria

- [ ] Ability to add a Git server via URL + token.
- [ ] Auto-detection of server type and API version.
- [ ] Display commits, branches, PRs/MRs in Huly interface.
- [ ] Webhook endpoint to receive real-time updates.
- [ ] Documentation with examples for GitLab and Gitea,.

### Additional Context

- GitLab API: `https://docs.gitlab.com/api/`
- Gitea API Swagger: `https://gitea.com/api/swagger`