- Add get_miner_id() dependency to extract miner ID from X-Miner-ID header
- Update miner register and heartbeat endpoints to require both X-Miner-ID and X-Api-Key headers
- Remove miner_id from query parameters in favor of header-based extraction
- Fix miner heartbeat CLI to send proper JSON payload with inflight, status, and metadata fields
- Fix typo in MinerService: extra_metadata → extra_meta_data