Add option to strip leading track numbers in upload titles

[nevotgnab]

Summary

Adds an optional bulk rename toggle in Upload Settings:

• Advanced Options → Strip leading track numbers
• When enabled, leading numeric prefixes are removed from generated titles
  • Examples: 01 Title, 01-01-01 Title, (01) 02 Title -> Title
• Default is off (no behavior change unless enabled)

Why

In real uploads (especially with weak/missing metadata), titles often include unwanted index prefixes.
Editing each track manually is tedious, so this adds a one-click cleanup step.

Behavior Change

• Before: Unknown Artist - 01 Supernova
• After (toggle ON): Unknown Artist - Supernova

Works for both filename-derived and metadata-derived title flows used in this dialog.

Tradeoff (Code Aesthetics)

A few implementation shapes were considered:

• A more “clean architecture” refactor (extract title builder + tests)
• Very minimal local patching inside existing switch logic

This PR intentionally chooses the smaller patch:

• keeps changes localized
• avoids large structural edits in non-owned code
• ships useful behavior quickly

Cost:

• code is not as “perfectly factored” as a dedicated refactor would be

Given scope, this is a pragmatic balance between readability and minimal churn.