feat(org): add MCP tools for organization-level labels (list/create/edit/delete) (#99) (#102)

This PR adds full support for managing organization-level labels via MCP. It uses the newly added SDK APIs now available on main branch, see https://gitea.com/gitea/go-sdk/issues/732.

Registers following tools under label module and wires them into the MCP server as read/write tools:

- list_org_labels: list labels defined at the organization level (pagination supported)
- create_org_label: create a label in an organization (name, color, description, exclusive)
- edit_org_label: edit an organization label (name, color, description, exclusive)
- delete_org_label: delete an organization label by ID

Dependency note:
go.mod/go.sum updated to use the SDK main branch pseudo-version that includes the org-label APIs.

If you prefer to merge only after a tagged SDK release, I can bump the dependency to the new tag as soon as it’s available.

Thanks for considering!

Reviewed-on: https://gitea.com/gitea/gitea-mcp/pulls/102
Reviewed-by: Bo-Yi Wu (吳柏毅) <appleboy.tw@gmail.com>
Co-authored-by: Daniel <danielwichers@gmail.com>
Co-committed-by: Daniel <danielwichers@gmail.com>

go.sum

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