Add manual trigger to docker-pr workflow for test builds

Adds workflow_dispatch trigger that allows:
- Manual workflow runs from GitHub Actions UI
- Optional push to registry (choice: true/false)
- Custom image tag (e.g., test, pr-13)

Normal PR behavior unchanged (push: false).
When manually triggered, can push test images to both:
- DockerHub: tzahi12345/youtubedl-material:<tag>
- GHCR: ghcr.io/voc0der/youtubedl-material:<tag>

.github/workflows/docker-pr.yml

@@ -3,6 +3,21 @@ name: docker-pr
 on:
   pull_request:
     branches: [master]
+  workflow_dispatch:
+    inputs:
+      push_image:
+        description: 'Push image to registry'
+        required: true
+        default: 'false'
+        type: choice
+        options:
+          - 'true'
+          - 'false'
+      image_tag:
+        description: 'Docker image tag (e.g., test, pr-13)'
+        required: true
+        default: 'test'
+        type: string
 
 jobs:
   build-and-push:
@@ -27,6 +42,33 @@ jobs:
         uses: docker/setup-qemu-action@v3
       - name: setup multi-arch docker build
         uses: docker/setup-buildx-action@v3
+
+      - name: Login to DockerHub
+        if: github.event.inputs.push_image == 'true'
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+      - name: Login to GitHub Container Registry
+        if: github.event.inputs.push_image == 'true'
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.repository_owner }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Set push and tag values
+        id: build_params
+        run: |
+          if [ "${{ github.event_name }}" = "workflow_dispatch" ]; then
+            echo "push=${{ github.event.inputs.push_image }}" >> $GITHUB_OUTPUT
+            echo "tags=tzahi12345/youtubedl-material:${{ github.event.inputs.image_tag }},ghcr.io/${{ github.repository_owner }}/youtubedl-material:${{ github.event.inputs.image_tag }}" >> $GITHUB_OUTPUT
+          else
+            echo "push=false" >> $GITHUB_OUTPUT
+            echo "tags=tzahi12345/youtubedl-material:nightly-pr" >> $GITHUB_OUTPUT
+          fi
+
       - name: build & push images
         uses: docker/build-push-action@v6
         with:
@@ -34,5 +76,5 @@ jobs:
           file: ./Dockerfile
           platforms: linux/amd64,linux/arm/v7,linux/arm64/v8
           #platforms: linux/amd64
-          push: false
-          tags: tzahi12345/youtubedl-material:nightly-pr
+          push: ${{ steps.build_params.outputs.push }}
+          tags: ${{ steps.build_params.outputs.tags }}