Some broadcasting software (e.g., Prism Live Studio) strips special characters from stream keys, making Owncast-generated keys incompatible. Changes: - Create separate STREAM_KEY_COMPLEXITY_RULES without special char requirement - Update generateRndKey() to only use alphanumeric characters - Keep PASSWORD_COMPLEXITY_RULES unchanged for admin password security - Update tooltip text to reflect new requirements - Add comprehensive tests for stream key generation Fixes #4690 Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>