fix: regenerate bun lockfiles and fix lint errors

Commit notes

- Regenerate backend/bun.lock to fix frozen-lockfile CI failures - Regenerate root bun.lock for workspace consistency - Fix lint errors in share-events.ts (use optional chaining, avoid non-null assertion) - Fix lint error in crypto.test.ts (use template literal instead of concatenation) - Apply auto-fixes from biome linter to various files

Co-authored-by: armin.naimi <[email redacted]>