fix: render same-origin gateway paths in token icons

[erubboli]

Problem

Bridge token icons still rendered as letter avatars even though the ipfs proxy served every metadata document and logo (15/15 HTTP 200 in the browser network log). Root cause: the bridge-sdk metadata pipeline resolves icons to same-origin gateway paths (/ipfs/), but safeImageUri only accepted absolute https:, ipfs: or data:image/ URIs — a relative path made new URL() throw, the icon resolved to null, and the picker rendered its fallback without ever creating an img element.

Fix

• safeImageUri now passes through same-origin paths that start with a single slash. Privacy posture unchanged: those URLs can only hit our own ipfs proxy, so no third-party fetch is possible. Protocol-relative and backslash forms stay rejected so a foreign host cannot be smuggled past the check.

Verification

• New tests: same-origin paths pass, // and backslash forms rejected; full suite 846 green, typecheck and build clean.