Implement wgpu-hal bridge for Bevy zero-copy integration (Phase 3.1)

Created wgpu-hal bridge infrastructure for Bevy plugin:

**New Dependencies**
- wgpu-hal 27: Hardware abstraction layer
- wgpu-types 27: Type definitions for format/usage conversion
- bevy: Moved to main dependencies under 'bevy' feature

**New Module: src/bevy_plugin/wgpu_bridge.rs**
- Format conversion: Geyser TextureFormat ↔ wgpu_types::TextureFormat
- Usage conversion: Geyser TextureUsage ↔ wgpu_types::TextureUsages
- WgpuTextureHandle: Safe wrapper for imported textures
- WgpuBackendType: Platform discrimination (Vulkan/Metal/D3D12/GL)
- Bidirectional format mapping with 20+ texture formats
  - 8-bit: RGBA8, BGRA8, sRGB variants, R8, RG8
  - 16-bit: R16/RG16/RGBA16 float, R16 uint/sint
  - 32-bit: R32/RG32/RGBA32 float/uint/sint
  - Depth: Depth32Float, Depth24Plus, Depth24PlusStencil8
  - HDR: RGB10A2, RG11B10
- Comprehensive unit tests for format/usage roundtrips

**Bridge Architecture**
- Platform-agnostic type system bridging Geyser ↔ wgpu
- External memory import foundation (marked NotImplemented)
- Designed for zero-copy texture sharing with Bevy render backend

**Updated Bevy Plugin**
- Export WgpuTextureHandle and WgpuBackendType
- Fixed Bevy 0.14 compatibility issues
  - Image creation without RenderAssetUsages
  - Extract system with proper types
  - Removed unused imports

**Error Handling**
- Added GeyserError::UnsupportedFormat for unknown formats
- Added GeyserError::NotImplemented for WIP features

**Status: Phase 3.1 - Foundation Complete**
- ✅ wgpu-hal integration scaffolding
- ✅ Format/usage conversion layer
- ✅ Safe handle wrapper types
- ⏳ External memory import (next: actual wgpu device integration)
- ⏳ Bevy render resource bridging (next step)

Compiles cleanly with --features bevy,vulkan
All format conversion tests pass

Author: vdmokstati