feat: add favorite button to DriftMemory widget

[luckydevil13]

Description

Adds a favorite (like) button to the DriftMemoryBottomInfo widget in the mobile app. When viewing a drift memory, users can now toggle the favorite status of the currently displayed asset directly from the bottom info bar, without leaving the memory view.

The widget was converted from StatelessWidget to ConsumerWidget to support Riverpod state management. The favorite button is only shown when the current user owns the asset (i.e., RemoteAsset with matching ownerId), and it correctly updates both the asset viewer state and the in-memory asset list.

How Has This Been Tested?

• Verified favorite button appears for own remote assets and is hidden for others' assets
• Tapped favorite button to add asset to favorites — icon turns red
• Tapped again to remove from favorites — icon returns to outline
• Confirmed state stays synced after navigating away and returning

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.

An LLM was used to assist with writing the initial implementation code for the favorite button logic in DriftMemoryBottomInfo.

[luckydevil13]

Could a maintainer please add the changelog:mobile label to this PR?

[alextran1502]

Thanks for the PR. We also have the mechanism to favorite a memory, which is currently displayed on the web as shown below

If we introduce this favorite button and its behavior differs from the web, it can be confusing. Do you have any proposals for making them more intuitive?

[luckydevil13]

@alextran1502 , alight to web implementation:

• move favorite button to top-right corner
• white infill color

[shenlong-tanwen]

@luckydevil13 The favourite button on the web saves the memory, i.e, updates the isSaved field on the memory and does not favourite the asset and the difference between the web and mobile might confuse the users is what @alextran1502 meant. The change looks good, but if we want to favourite the asset displayed on the memory and not the memory itself, we might need to find a way for both of the features to exist together

[luckydevil13]

@shenlong-tanwen @alextran1502 do I miss something...

For Web

1. Every day the server generates "on this day" memories from past years
2. They're shown only today
3. After 30 days they're deleted from the DB (not the photos, just the grouping)
4. isSaved = true means the grouping won't be deleted, it survives cleanup

What the user sees visually:

• Heart icon is filled or outlined - that's it? nothing more?
• Next year on the same day the server will recreate the memory from the same photos anyway, so the difference is minimal
  Conclusion: the isSaved flag is a pretty narrow feature. Visually it only affects the button icon. The practical benefit is questionable since memories are regenerated every year anyway.

And we need to deside

• Replace save memory with favorite (on web)
• Or add two separate buttons

[alextran1502]

• The heart icon on the memory on the web is for favoriting the memory.
• The heart icon you added on the mobile app is for favoriting an asset.

I think you might have thought that the heart icon on the memory page on the web also favoriting an asset

[luckydevil13]

@alextran1502 thanks,

What is scenario with favoriting the memory? for me it's strage to have two "favorites", I've expect ❤️ is favorites

[alextran1502]

@luckydevil13 We plan to introduce a memories view where the favorite memories can be filted or displayed on top