fix(ble): parse Self-ID messages and feed them to the tracker

[wnagele]

What

ble_feeder.py silently drops Self-ID messages (ODID type 0x3): the BLE decoder has no parser for the type and no route into the tracker, so drones detected over BLE never surface their free-text purpose of flight. This adds the missing parser and wires it end-to-end.

Why

Self-ID is one of the four core ASTM F3411 broadcast messages and the only way a drone tells observers what it is doing ("Photography Lesson", "Search and Rescue", …). dump3411 already surfaces it everywhere — journal, JSON feed (self_id / self_id_seen), MQTT per-drone state, dashboard Description column — but only for WiFi-carried detections, since wifi_feeder.py already parses the type. For BLE-carried detections the tracker was never told; at best --verbose logged an empty Type=Self ID line.

How

• parse_self_id() in ble_feeder.py decodes the 25-byte ODID Self-ID message per ASTM F3411-22a: description_type (byte 1) and the NUL-padded ASCII description (bytes 2–25). Mirrors wifi_feeder.parse_self_id, which holds the full byte-layout commentary.
• decode_rid_message() now dispatches message type 0x3 to it.
• BLEFeeder._update_tracker() routes decoded Self ID messages to Tracker.update_self_id(...) with rid_source="ble", matching the existing Basic ID / Location / System / Operator-ID routes.

No feed or schema changes — the self_id fields already existed; this populates them from BLE.