MD5 Verdict Cache — Instant Repeat-Image Results

• verdict_cache table: MD5-keyed cache of AI moderation verdicts (image_hash → verdict JSON)
• Repeat images skip the OpenAI call entirely — returns cached verdict in <50ms vs 1-5s
• Cache hit tracked on last_accessed; cold cache warms on first /v1/process call per image
• Billing unchanged — cached calls still count as billable (compliance record kept)