#191 [Feature]: User-uploaded custom piece sets

[Anonymous]

Originally created by: BilgeGates
Originally owned by: BilgeGates

What problem does this solve?

Coaches and content creators who have their own piece images cannot use them in ChessVision. The app is limited to the built-in Lichess piece sets, with no way to bring custom visuals.

Proposed solution

Allow users to upload a ZIP file containing SVG or PNG piece images named by piece identifier (wK.svg, bQ.svg, etc.). The app validates the set, registers it locally, and makes it selectable from the piece set picker alongside existing sets. Uploaded sets persist via syncStorage for signed-in users.

Context

Sub-issue of [#162] — custom and fairy piece sets. Scope: user-uploaded sets only; built-in fairy glyphs are tracked in [#190], themed packs in [#192].

Before submitting

• [x] I searched existing requests and this is not a duplicate.

[Anonymous]

• assigned_to: BilgeGates