feat(portable): load per-customer payload from a PE resource

Customizing a Windows client recompiled the packer for every customer,
because data.bin was baked in with include_bytes!. The generic payload is
identical across customers, so only the small per-customer delta needs to
vary: the branded runner exe, custom.txt and the icons.

The packer now also reads an RDPKG RCDATA resource holding a second blob in
the same format, and folds it over the compiled-in payload. A build can then
inject that resource into a prebuilt template instead of running cargo.

The executable to launch comes from the package trailer, and the extraction
directory follows its stem, which replaces the sed of APP_PREFIX. Where the
executable itself is not customized (sciter x86) it stays in the generic
payload and is only renamed, so the merge covers both shapes.

custom.txt keeps being written to disk next to the app: that is what the
client reads at startup and what the updater stages so a customization
survives an upgrade to a stock build.

Also fixes generate.py restoring os.curdir (the literal ".") instead of the
previous working directory, which left it inside the source folder.

CI: ship windows-aarch64 in the unsigned tarball, so ARM custom clients have
a template to build from.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Q7fBdTwziR5BHTkSz7Tzcm

.github/workflows/flutter-build.yml

@@ -919,6 +919,12 @@ jobs:
           name: rustdesk-unsigned-windows-x86_64
           path: ./windows-x86_64/
 
+      - name: Download Artifacts
+        uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
+        with:
+          name: rustdesk-unsigned-windows-aarch64
+          path: ./windows-aarch64/
+
       - name: Download Artifacts
         uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
         with:
@@ -927,7 +933,7 @@ jobs:
 
       - name: Combine unsigned app
         run: |
-          tar czf rustdesk-${{ env.VERSION }}-unsigned.tar.gz *.dmg windows-x86_64 windows-x86
+          tar czf rustdesk-${{ env.VERSION }}-unsigned.tar.gz *.dmg windows-x86_64 windows-aarch64 windows-x86
 
       - name: Publish unsigned app
         uses: softprops/action-gh-release@de2c0eb89ae2a093876385947365aca7b0e5f844 # v1