feat(ui): draggable titlebar, hub search loading, workflow pipelines, and ASD-STE100 documentation

[spelech]

Summary

This pull request implements key UI usability improvements, reorganization, and documentation:

1. Draggable Window Taskbar / Titlebar:

   • Added a 34px custom titlebar with app icon, version badge, draggable grip, double-tap window maximize/restore, and minimize, maximize/restore, and close buttons.
   • Restored dragging capabilities when extending the client area into decorations (ExtendClientAreaToDecorationsHint="True").

2. Hugging Face Hub Search Feedback:

   • Added IsLoading / IsModalLoading states to HuggingFaceSearchViewModel.
   • Added visual loading progress bars, busy indicators on the search button, and clear feedback messages during model queries.

3. CivitAI Starter Recommendations & Suggestions:

   • Populated CivitAI Hub with curated starter models (e.g., SDXL Base 1.0, Flux.1 Dev, Realistic Vision V6.0, DreamShaper XL) on initial load instead of presenting a blank view.
   • Added quick suggestion filter chips (All, Checkpoints, LoRA, SDXL, Flux.1) and loading indicator.

4. Streamlined Tab Hierarchy & Workflow Pipelines:

   • Restructured top-level tabs into 5 clean categories:
     • 📦 Models: Consolidated Downloaded/Manage Models, Hugging Face Hub, and CivitAI Hub into sub-tabs.
     • ⚡ Workflows: Segmented generation workflows for 🎨 Images, 💬 Text, 🎬 Video, 📦 3D Mesh, and 🎵 Audio. Each workflow features a sequential Step 1 ➔ Step 2 ➔ Step 3 ➔ Step 4 pathway indicator and clear controls.
     • ⚡ Can I Run It: Hardware fit and pre-flight calculator.
     • 📖 Documentation: In-app ASD-STE100 technical documentation.
     • ⚙️ Settings: Configuration and tools.

5. In-App ASD-STE100 Documentation:

   • Created DocumentationViewModel and DocumentationTabControl providing standardized Simplified Technical English procedures for:
     • Image Generation Flow (SDXL / Forge)
     • Text Generation Flow (Ollama / Local LLM)
     • Video Generation Flow (ComfyUI DiT)
     • Audio & SFX Generation Flow (Stable Audio / Kokoro)
     • 3D Mesh Generation Flow (TRELLIS / ComfyUI 3D)
     • Models Hub Management & Downloads
     • Can I Run It Hardware Fit Calculator
     • Engine & VRAM Troubleshooting

Verification

• Linting: npm run lint passed (0 errors).
• Typecheck: npx tsc --noEmit passed (0 errors).
• Unit & UI Tests: dotnet test LocalLLMServerManager.sln passed (593 passed, 0 failed, 1 skipped screenshot generator).