fix: include pre-built device_page/dist in resources to fix empty Filament Manager

The `resources/web/device_page/dist/` directory was excluded from the
repository by the `**/dist/` gitignore rule.  All other web assets in
`resources/web/` are pre-built static files committed directly to git,
but `device_page/dist/` was only generated at CMake build time and never
packaged into the Linux AppImage or macOS DMG releases.

Add a gitignore exception to track `resources/web/device_page/dist/` and
commit the pre-built assets (index.html, assets/index.{css,js}, img/**).
This mirrors how all other embedded web pages in BambuStudio are shipped.

The CMake `device_page_build` target will still rebuild these files on a
full source build; the committed dist serves as the fallback that release
packages rely on.

Closes #10799
Closes #10806

Author: BenJule

.gitignore

@@ -38,4 +38,7 @@ compile_commands.json
 **/node_modules/
 .worktrees/
 **/dist/
+# Pre-built web assets for Filament Manager — committed so release packages include them
+!resources/web/device_page/dist/
+!resources/web/device_page/dist/**