feat(ui): support batch rename of multiple projects

[CalvinAllen]

Description

Allow renaming multiple projects at once, either through multi-select or a batch rename dialog.

Current Behavior

The extension renames one project at a time. Users must repeat the process for each project they want to rename.

Proposed Changes

Option A: Multi-Select Support

• Detect when multiple projects are selected in Solution Explorer
• Show a dialog to enter new names for each selected project
• Process all renames in sequence

Option B: Batch Rename Dialog

• Add a new command "Batch Rename Projects"
• Show a dialog listing all projects with editable names
• Allow user to modify names for projects they want to rename
• Process all changed names

UI Mockup (Option B)

┌─────────────────────────────────────────────┐
│ Batch Rename Projects                       │
├─────────────────────────────────────────────┤
│ Current Name          │ New Name            │
│───────────────────────┼─────────────────────│
│ OldProject1           │ NewProject1         │
│ OldProject2           │ [unchanged]         │
│ OldProject3           │ NewProject3         │
├─────────────────────────────────────────────┤
│                        [Cancel] [Rename]    │
└─────────────────────────────────────────────┘

Considerations

• Need to handle cross-references between renamed projects
• Order of operations matters if projects reference each other
• Progress dialog should show overall progress across all projects

Priority

Low - convenience enhancement