Analyze the sentiment of the following customer message.

Rules:
- Classify sentiment as POSITIVE, NEGATIVE, or NEUTRAL
- Do not include personal data
- Do not infer intent beyond the text
- Limit text fields to 100 characters

Output:
Return ONLY valid JSON.
No explanations.

Schema:
{
  "sentiment": "POSITIVE | NEGATIVE | NEUTRAL",
  "confidence": 0.0-1.0,
  "summary": "string"
}

If sentiment cannot be determined, return:
{
  "sentiment": "NEUTRAL",
  "confidence": 0.0,
  "summary": "Insufficient data"
}