feat(web): group albums by name prefix

[hitzhangjie]

Description

Adds a Group by name option on the albums page. Albums are grouped by the first segment of the album name, split on a configurable delimiter (default -).

• Names with a delimiter use the prefix as the group key (旅游-日本 → 旅游).
• Names without a delimiter use the full name, so aigc and aigc-videos land in the same aigc group.
• Names with an empty prefix (e.g. -日本) go into Uncategorized.
• When this grouping is selected, a small input lets you change the delimiter (falls back to - if left empty).

No existing issue.

How Has This Been Tested?

• Unit tests for parseAlbumNameGroup / getAlbumGroupDelimiter (web/src/lib/utils/album-name-group.spec.ts)
• Manual: Albums page → group by name → albums with a shared prefix appear together
• Manual: Change the delimiter in the albums toolbar and confirm groups update
• Manual: Sharing page still loads albums with default view settings

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.

• The analysis (which part should be modified) before create this PR is done by LLM;
• The code in this PR is written by LLM;
• The testing code in this PR is written by LLM;
• The PR description is drafted by LLM;
• And this PR is already tested mannually;

[hitzhangjie]

Here's a screenshot:

[bo0tzz]

Please fill out the LLM disclosure more completely. "The code on this branch was already committed" handwaves a pretty important part.

[immich-push-o-matic]

Label error. Requires exactly 1 of: changelog:.*. Found: 🖥️web. A maintainer will add the required label.