Add Snapshot Capture

[mfaferek93]

Summary

Capture topic data when fault confirmed for debugging.

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Proposed solution (optional)

Configuration:

fault_manager:
  snapshots:
    default_topics: [/odom, /battery_state]
    fault_patterns:
      "MOTOR_.*": [/joint_states, /cmd_vel]

On confirmation: subscribe, capture, store as JSON.
Database:

sqlCREATE TABLE snapshots (
  fault_code TEXT,
  topic TEXT,
  data TEXT,
  captured_at INTEGER
);

Add GetSnapshot.srv and endpoint.

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Additional context (optional)

• 1 second timeout per topic
• Size limit per message
• Handle missing topics