chore: remove 5 unused frontend dependencies

[ajianaz]

Summary

web/package.json carries 5 runtime dependencies that are not imported anywhere in web/src:

• svelte-sonner
• vaul-svelte
• embla-carousel-svelte
• formsnap
• sveltekit-superforms

(Verified via grep across web/src excluding .svelte-kit.)

Impact

• Bigger install + lockfile, larger attack surface, misleading signals for contributors auditing the stack.

Fix

bun remove (or npm equivalent) the five packages. Note: if the toast issue opts for a svelte-sonner migration, remove the other four only and keep svelte-sonner.

Acceptance criteria

• grep -r "svelte-sonner\|vaul\|embla\|formsnap\|superforms" web/src shows no imports (or only the intentionally-kept one).
• Lockfile updated, build clean.

Source: Titen UX audit 2026-09-20 (finding L5).

[ajianaz]

Implemented in PR #278 (merged 2026-09-20, commit 57c101f) — UX audit remediation batch.