Implement nightly VERSION automation using PlatformIO script

- Created pio-scripts/set_nightly_version.py following existing set_version.py pattern
- Script sets VERSION to yymmddb format with build number 0 for nightly builds
- Modified build.yml to accept nightly_build boolean input
- Modified nightly.yml to pass nightly_build=true flag
- Added set_nightly_version.py to platformio.ini extra_scripts
- Uses WLED_NIGHTLY_BUILD environment variable to conditionally set VERSION

Co-authored-by: softhack007 <91616163+softhack007@users.noreply.github.com>

.github/workflows/build.yml

@@ -4,10 +4,11 @@ name: PlatformIO CI
 on:
   workflow_call:
     inputs:
-      version:
-        description: 'Build VERSION in format yymmddb (optional, for nightly builds)'
+      nightly_build:
+        description: 'Flag to indicate this is a nightly build'
         required: false
-        type: string
+        type: boolean
+        default: false
 
 jobs:
 
@@ -67,7 +68,7 @@ jobs:
     - name: Build firmware
       env:
         WLED_RELEASE: True
-        PLATFORMIO_BUILD_FLAGS: ${{ inputs.version && format('-D VERSION={0}', inputs.version) || '' }}
+        WLED_NIGHTLY_BUILD: ${{ inputs.nightly_build && 'true' || 'false' }}
       run: pio run -e ${{ matrix.environment }}
     - name: Rename Bin
       run: mv -v .pio/build/${{ matrix.environment }}/firmware.bin firmware-${{ matrix.environment }}.bin