Create or bulk-create tracked prompts

Track AI-visibility prompts. CONSUMES CREDITS (each prompt is run against the AI platforms): always ask the user for permission before calling this. Single mode: creates one prompt and returns its record. Bulk mode: pass items array to create multiple at once. isEnabled, isBranded and region apply to prompt and are also the defaults for every entry in items, so bulk callers set them once at the top level.