Implemented automatic version generation that creates versions in the format
v{YEAR}.{MMDD}.{INCREMENT}, removing the need for manual version input.

## Changes

### 1. Auto-Increment Version Generation (lines 25-60)

**New job: `generate-version`**
- Runs first, before any other jobs
- Generates version automatically based on current UTC date
- Format: `v2025.1204.0` (year.monthday.increment)
- Checks existing tags for today's date
- Auto-increments if multiple releases on same day
- Outputs version for downstream jobs

**Algorithm:**
```bash
DATE_VERSION=$(date -u '+%Y.%m%d')           # e.g., 2025.1204
EXISTING_TAGS=$(git tag -l "v${DATE_VERSION}.*")
if [ -z "$EXISTING_TAGS" ]; then
  INCREMENT=0                                # First release today
else
  LAST_INCREMENT=$(extract from last tag)    # e.g., extract 0 from v2025.1204.0
  INCREMENT=$((LAST_INCREMENT + 1))          # Increment to 1
fi
VERSION="v${DATE_VERSION}.${INCREMENT}"      # e.g., v2025.1204.0
```

### 2. Removed Manual Version Input (lines 3-10)

**Before:**
```yaml
inputs:
  version:
    description: 'Release version (e.g., v3.5.0)'
    required: true
```

**After:**
```yaml
inputs:
  prerelease:
    description: 'Mark as pre-release'
    required: false
    type: boolean
    default: false
```

Only prerelease flag remains - version is now automatic!

### 3. Updated All Job Dependencies (throughout file)

**create-release job:**
- Now depends on `generate-version`
- Passes version through outputs to downstream jobs
- Lines 62-100

**build-binaries job:**
- Uses `needs.create-release.outputs.version` instead of `inputs.version`
- Asset names constructed dynamically
- Lines 102-214

**build-docker job:**
- Uses `needs.create-release.outputs.version` for checkout and tags
- Lines 216-256

**finalize-release job:**
- Uses `needs.create-release.outputs.version` for documentation
- Lines 258-373

### 4. Updated Asset Names (lines 110-119)

**Before:**
```yaml
asset_name: fluffos-${{ inputs.version }}-windows-x86_64.zip
```

**After:**
```yaml
asset_suffix: windows-x86_64.zip
# Asset name constructed at runtime: fluffos-${VERSION}-windows-x86_64.zip
```

## Version Examples

| Date | Previous Tags | New Version |
|------|--------------|-------------|
| Dec 4, 2025 | None | v2025.1204.0 |
| Dec 4, 2025 | v2025.1204.0 | v2025.1204.1 |
| Dec 4, 2025 | v2025.1204.0, v2025.1204.1 | v2025.1204.2 |
| Dec 5, 2025 | (from prev day) | v2025.1205.0 |
| Jan 1, 2026 | None | v2026.0101.0 |

## Benefits

✅ **No manual input** - Just click "Run workflow"
✅ **No version conflicts** - Auto-increments if tag exists
✅ **Date-based** - Easy to see when release was made
✅ **SemVer compatible** - Format works with semver parsers
✅ **Supports multiple releases per day** - Increment handles it
✅ **Deterministic** - Same date = same base version

## Usage

**Old workflow:**
1. Go to Actions → Release
2. Click "Run workflow"
3. **Enter version: v3.5.0**
4. Select prerelease (optional)
5. Run

**New workflow:**
1. Go to Actions → Release
2. Click "Run workflow"
3. ~~Enter version~~ (REMOVED!)
4. Select prerelease (optional)
5. Run → **Version auto-generated!**

## Testing

- ✅ YAML syntax validated
- ✅ All version references updated
- ✅ No `inputs.version` references remain
- ✅ Job dependencies correctly configured
- ✅ Version generation logic tested

**Next release will be:** `v2025.1205.0` (or higher if run multiple times)