v1.31.0

Feature

• Add deep dark theme (#728)
• Add debounced search refresh for filtered views on new messages

Chore

• Make read/unread message state clearly distinguishable (WCAG AA)
• Add accessible names to icon-only buttons and fix sender tag mismatch
• Update Go dependencies
• Update node dependencies
• Update caniemail test database
• Update GitHub Actions

Fix

• Include all IANA special-use IPv4 ranges in IsInternalIP check
• Prevent SMTP command injection via drainData fragment-boundary bypass
• Validate Send API custom header keys per RFC 5322