fix(server): restore access to existing worktrees

[enisze]

What Changed

• Restored discovery and access for existing worktrees across server, web, and mobile clients.
• Added per-project worktree branch prefixes with persistence, migration, projection, and creation support.
• Updated GitHub authentication handling to parse current CLI output and scope Git credentials per account.
• Improved terminal, WebSocket, orchestration, and source-control behavior for recovered worktrees.
• Updated focused tests and fixtures across affected surfaces.

Why

Existing worktrees could become inaccessible after initialization or recovery because project metadata, branch naming, and source-control authentication were not consistently preserved across projections and clients. This change restores access while keeping generated branches aligned with project configuration and supporting current GitHub CLI authentication output.

UI Changes

The web and mobile clients now carry the restored project/worktree metadata through project and thread flows. No user-facing screenshots are included because the changes primarily restore existing functionality and do not introduce a new visual design.

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes
• I included a video for animation/interaction changes