ci: refactor workflows to use reusable workflow calls

Updated build workflows to use workflow_call triggers and accept ci_version as input, removing inline CI version generation. Upgraded all actions to v5 and added a new build.yml workflow to orchestrate builds for AppImage, Steam Link, and Windows/macOS using reusable workflows. This improves maintainability and consistency across CI jobs.

.github/workflows/build-steamlink.yml

@@ -1,38 +1,40 @@
-name: Build Steam Link
+---
+name: Build - Steam Link
+permissions:
+  contents: read
 
 on:
-  push:
-  pull_request:
-    branches: [ "master" ]
+  workflow_call:
+    inputs:
+      ci_version:
+        required: true
+        type: string
 
 jobs:
   build:
+    env:
+      CI_VERSION: ${{ inputs.ci_version }}
     runs-on: ubuntu-22.04
 
     steps:
       - name: Checkout Repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
         with:
           submodules: 'recursive'
           fetch-depth: 1
 
       - name: Checkout Steam Link SDK
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
         with:
           repository: ValveSoftware/steamlink-sdk
           path: steamlink-sdk
           fetch-depth: 1
 
-      - name: Set CI version
-        run: |
-          CI_VERSION=`echo $GITHUB_SHA | cut -c1-6`
-          echo "CI_VERSION=$CI_VERSION" >> $GITHUB_ENV
-
       - name: Build binaries
         run: STEAMLINK_SDK_PATH=$PWD/steamlink-sdk scripts/build-steamlink-app.sh
 
       - name: Upload Binaries
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v5
         with:
           name: Moonlight-SteamLink-${{ env.CI_VERSION }}
           path: build/deploy-release/*