fix: chat-delegate logs full state data at INFO level causing excessive log sizes

[sanity]

Problem

The chat-delegate logs the full value byte array at INFO level on every store request:

// delegates/chat-delegate/src/handlers.rs:18-21
logging::info(
    format!("Delegate received StoreRequest key: {key:?}, value: {value:?}").as_str(),
);

With Debug formatting, a 300KB state becomes a ~1MB log line because each byte prints as [167, 109, 99, ...]. This causes:

• 25MB+ of logs per hour on active nodes
• Log lines up to 316KB each
• Diagnostic reports failing to upload (413 Payload Too Large)

Suggested Fix

Either:

1. Change to DEBUG level instead of INFO
2. Truncate the value in the log: value: [{} bytes]
3. Log only a hash/summary of the value

Example fix:

logging::info(
    format!("Delegate received StoreRequest key: {key:?}, value: [{} bytes]", value.len()).as_str(),
);

Workaround

freenet/freenet-core adds log size limits in diagnostic reports (10KB per line, 2MB total), but the underlying verbosity should still be fixed to reduce disk usage and improve log readability.

[AI-assisted - Claude]