Harden lyrics search and resolve audit findings

[variablenix]

Summary

• harden Genius authentication, redirect handling, result URL validation, and IRC-safe output formatting
• preserve one complete Genius lyrics link, including a bounded short-link fallback for unusually long canonical URLs
• add regression coverage for all reported Electric Wizard and Snoop Dogg query forms and upstream failure modes
• resolve repository-wide static-analysis findings discovered during the audit
• document the lyrics output and token-handling guarantees

Validation

• go test -count=1 -race ./...
• go vet ./...
• go build ./...
• go test -cover ./...
• staticcheck ./...
• govulncheck ./... (no vulnerabilities found)
• focused gosec scan (0 actionable issues after reviewing documented false-positive categories)
• go mod verify
• go mod tidy -diff
• git diff --check