fix(web): keep upload totals stable when dismissing items (#27247)

[Nicolas-micuda-becker]

Description

This PR fixes a regression introduced in #27139 where successful uploads were automatically removed from the overlay and their counters decremented to zero after upload completion, making it impossible to track how many files were successfully uploaded in a session.

The problem:
In version 2.6.2, once an upload batch completes, successful uploads automatically disappear from the overlay and are decremented from both the "Uploaded" and "Total" counters. Only errors and duplicates remain visible.

Root cause:
The removeItem() function in web/src/lib/stores/upload.ts was decrementing stats.success and stats.total when removing successful items, treating these as "remaining items" counters rather than "session totals."

The solution:

• removeItem() no longer decrements stats.success or stats.total for successfully uploaded items
• Only stats.errors and stats.duplicates are decremented when users manually dismiss items from the overlay
• This keeps "Uploaded" and "Processed/Total" as stable session totals, while "Errors" and "Duplicates" reflect the items remaining in the overlay

Fixes #27247

How Has This Been Tested?

Test environment:

• OS: Ubuntu 25.04
• Immich version: v2.6.2
• Development setup: make dev (http://localhost:3000)
• Browser: Firefox 148.0

Steps to reproduce and verify the fix:

1. Started local dev environment with make dev
2. Uploaded 21 photos to the web interface at http://localhost:3000
3. Upload completed with the following results:
   • 17 successful uploads
   • 2 duplicates
   • 2 errors
4. Before fix (v2.6.2):
   • After upload completion: "0 successful, 2 errors, 2 duplicates, 4/4 processed"
   • The 17 successful uploads were automatically decremented
   • Total was reduced from 21 to 4 (only errors + duplicates remained)
   • Result: Impossible to know how many files were actually uploaded
5. After fix:
   • After upload completion: "17 sent, 2 errors, 2 duplicates, 21/21 processed"
   • Successful uploads remain counted even after being removed from the overlay
   • Total stays at 21 (the actual number of files processed)
   • Result: Clear session summary showing all processed files
6. Clicked the X button to remove 1 duplicate from the overlay
7. Counter correctly updated to: "17 sent, 2 errors, 1 duplicate, 21/21 processed"

The fix was also verified by running pnpm run format -> "All matched files use Prettier code style!"

Screenshots (if appropriate)

No screenshots needed - the bug and fix are behavioral (counter stability).

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.

Not used.

[danieldietzler]

This is pretty weird though. Now the counters for duplicates and errors match the entries in the list; the successful one doesn't. IMO that's unintuitive too