feat(mobile): enable local motion photo playback

[dnplkndll]

Description

Enables local (on-device) motion photos and live photos to play in the asset viewer. Previously only remote assets triggered the video component — assets with a local copy never animated.

This is a cleaned-up version of the work started by @LeLunZ in draft PR #26784. The prerequisite playbackStyle infrastructure from that series (#26541, #26596, #26747) was merged but the motion photo playback follow-up was left as a draft. This PR completes that work, resolves a circular dependency in base_asset.model.dart that appeared after the infrastructure landed, and polishes it for submission. All credit for the core approach goes to @LeLunZ.

Fixes #23525

video_viewer.widget.dart

• Check videoAsset.isMotionPhoto to select the right local file: motion assets use getMotionFileById (fetches the paired subtype via originFileWithSubtype), regular videos use getFileForAsset

thumbnail_tile.widget.dart

• Changed the live-photo badge check from asset is RemoteAsset && asset.livePhotoVideoId != null to asset.isMotionPhoto — shows the icon for local motion photos too

storage.repository.dart

• Extracted getMotionFileById(String assetId) from getMotionFileForAsset(LocalAsset asset) so the viewer can call it with a raw ID (needed when the resolved asset is a RemoteAsset with a localId)

base_asset.model.dart

• Fixed circular dependency: isMotionPhoto delegates to playbackStyle; playbackStyle uses livePhotoVideoId != null directly
• Added doc comment covering both remote (livePhotoVideoId) and local (resolved playback style) paths

Happy to make any changes before merging. @LeLunZ — if there was anything else you had planned for the original PR, please let me know and I'll incorporate it.

How Has This Been Tested?

• Verified local motion photos animate in the asset viewer on iOS (iPhone 15 Pro, iOS 18)
• Verified live photo badge appears on local-only motion photos in the timeline grid
• Full unit test suite (701 tests) passes with no regressions

Screenshots (if appropriate)

Checklist:

• I have carefully read CONTRIBUTING.md
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation if applicable
• I have no unrelated changes in the PR.
• I have confirmed that any new dependencies are strictly necessary.
• I have written tests for new code (if applicable)
• I have followed naming conventions/patterns in the surrounding code
• All code in src/services/ uses repositories implementations for database calls, filesystem operations, etc.
• All code in src/repositories/ is pretty basic/simple and does not have any immich specific logic (that belongs in src/services/)

Please describe to which degree, if any, an LLM was used in creating this pull request.

Claude (claude-sonnet-4-6) was used to assist with code review, refactoring suggestions, and drafting the PR description. All code changes were reviewed and tested manually on device.

[immich-push-o-matic]

Label error. Requires exactly 1 of: changelog:.*. Found: 📱mobile, llm-generated. A maintainer will add the required label.

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[github-actions]

Thank you for your interest in contributing to Immich! Unfortunately this PR looks like it was generated using an LLM. As noted in our CONTRIBUTING.md, we request that you don't use LLMs to generate PRs as those are not a good use of maintainer time.