Add game version management system with manifest support

Features:
- Version dropdown in single/ZIP upload (9.3.0, 9.2.0, etc.)
- Patch-compatible matching (9.3.x assets work with 9.3.0)
- manifest.json/xml support for automatic metadata detection
- Smart category auto-detection from folder structure
- Version field stored in GameAssets table

Manifest support:
- JSON format with gameVersion, category, assets array
- Per-file metadata overrides (type, required, description)
- Auto-detect falls back if no manifest present
- See ASSET-MANIFEST-SPECIFICATION.md for full spec

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

ASSET-MANIFEST-SPECIFICATION.md

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+# RR3 Asset Manifest Specification
+
+## Overview
+When uploading ZIP files to the RR3 Community Server, you can include a `manifest.json` or `manifest.xml` file to automatically configure asset metadata, version, and categorization.
+
+## File Format Options
+
+### Option 1: JSON Format (Recommended)
+Place `manifest.json` in the root of your ZIP file:
+
+```json
+{
+  "version": "9.3.0",
+  "gameVersion": "9.3.0",
+  "description": "Porsche Pack - 911 Models",
+  "author": "CommunityModder",
+  "category": "cars",
+  "assets": [
+    {
+      "file": "porsche/911_turbo.dat",
+      "category": "cars/porsche",
+      "type": "Model",
+      "required": true,
+      "description": "Porsche 911 Turbo model"
+    },
+    {
+      "file": "textures/911_turbo_paint.tex",
+      "category": "textures/cars",
+      "type": "Texture",
+      "required": false
+    }
+  ]
+}
+```
+
+### Option 2: XML Format
+Place `manifest.xml` in the root of your ZIP file:
+
+```xml
+<?xml version="1.0" encoding="UTF-8"?>
+<AssetManifest>
+  <Version>9.3.0</Version>
+  <GameVersion>9.3.0</GameVersion>
+  <Description>Porsche Pack - 911 Models</Description>
+  <Author>CommunityModder</Author>
+  <Category>cars</Category>
+  <Assets>
+    <Asset>
+      <File>porsche/911_turbo.dat</File>
+      <Category>cars/porsche</Category>
+      <Type>Model</Type>
+      <Required>true</Required>
+      <Description>Porsche 911 Turbo model</Description>
+    </Asset>
+    <Asset>
+      <File>textures/911_turbo_paint.tex</File>
+      <Category>textures/cars</Category>
+      <Type>Texture</Type>
+      <Required>false</Required>
+    </Asset>
+  </Assets>
+</AssetManifest>
+```
+
+## Field Descriptions
+
+### Root Fields
+- **version**: Asset pack version (e.g., "1.0.0")
+- **gameVersion**: RR3 game version this pack is for (e.g., "9.3.0")
+- **description**: Brief description of the asset pack
+- **author**: Creator name (optional)
+- **category**: Default category if not specified per-asset
+
+### Asset Fields
+- **file**: Relative path to file within ZIP (required)
+- **category**: Asset category (overrides root category)
+- **type**: Asset type (Data, Texture, Audio, Model, Config)
+- **required**: Whether clients must download this (true/false)
+- **description**: Brief description (optional)
+
+## Game Version Format
+- Use semantic versioning: `MAJOR.MINOR.PATCH`
+- Examples: `9.3.0`, `9.3.1`, `10.0.0`
+- **Compatibility**: Patch versions are compatible (9.3.x works with 9.3.0)
+
+## Categories
+Standard categories:
+- `base` - Core game files
+- `cars` - Car models and data
+- `tracks` - Track models and data
+- `audio` - Sound effects and music
+- `textures` - Texture files
+- `ui` - User interface elements
+- `events` - Event configurations
+- `dlc` - Downloadable content
+- `updates` - Game updates
+
+Subcategories allowed (e.g., `cars/porsche`, `tracks/silverstone`)
+
+## Asset Types
+- `Data` - Generic data files (.dat, .pak, .z)
+- `Texture` - Texture files (.tex, .dds, .png)
+- `Audio` - Audio files (.ogg, .mp3, .wav)
+- `Model` - 3D model files (.nct, .obj)
+- `Config` - Configuration files (.json, .xml)
+
+## Automatic Detection Fallback
+If no manifest file is provided, the server uses smart detection:
+1. Searches folder names for keywords (cars, tracks, audio, etc.)
+2. Preserves folder structure as subcategories
+3. Falls back to first folder name if no keywords match
+4. Version defaults to manual selection or "unknown"
+
+## Example ZIP Structure
+
+```
+my-asset-pack.zip
+├── manifest.json          # Metadata file
+├── cars/
+│   ├── porsche/
+│   │   ├── 911_turbo.dat
+│   │   └── 911_gt3.dat
+│   └── ferrari/
+│       └── 488_gtb.dat
+└── textures/
+    └── cars/
+        └── paint_textures.pak
+```
+
+## Upload Behavior
+1. Server extracts ZIP to temp location
+2. Searches for `manifest.json` or `manifest.xml` in root
+3. If found: Uses metadata from manifest
+4. If not found: Uses smart folder detection
+5. Processes each file according to configuration
+6. Calculates MD5/SHA256 hashes automatically
+7. Stores in database with version + category info
+
+## Version Compatibility
+When a game client requests assets:
+- Client sends version: `9.3.1`
+- Server returns assets for: `9.3.0`, `9.3.1` (patch-compatible)
+- Server excludes: `9.2.x`, `9.4.x`, `10.x.x`
+
+Major/minor versions must match exactly, patch versions are compatible within the same minor version.
+
+## Best Practices
+1. Always include a manifest file for large packs
+2. Use semantic versioning for both pack and game version
+3. Mark base game assets as `required: true`
+4. Use descriptive categories and subcategories
+5. Include author information for community tracking
+6. Test with single-file upload before bulk ZIP upload
+7. Use JSON format for better tool support