feat: add deterministic account avatars across wallet account surfaces

[alez04]

Summary

Implements issue #88 by introducing deterministic account avatars and showing them anywhere users choose or review wallet accounts.

What changed

• Added boring-avatars dependency.
• Added a reusable AccountAvatar component:
  • Deterministic by account identity (+ name seed fallback behavior already supported in component)
  • Uses wallet-aligned palette centered on primary cyan (#1ADEF5) with complementary tones
  • Uses marble variant
  • Supports watch-only badge overlay
• Replaced generic account icon / text-only account rows with avatars in:
  • App header active account selector
  • Home account dropdown list
  • Manage Accounts list items
  • dApp approval drawer account sections

UX details

• Avatars are consistent across views for the same account identity.
• Watch-only accounts preserve their visual indicator.
• Spacing in the home dropdown account rows was adjusted so avatar/text alignment is clear.

Validation

• bun run lint ✅
• bun run build ✅

Related

• Closes feat: generate unique avatars for accounts #88