feat(transit): add Lisbon's Carris Metropolitana buses

Keyless GTFS-Realtime feed from Carris Metropolitana, documented in the
operator's public API repository. No licence is stated for the realtime
endpoint (the static GTFS is CC BY 4.0), so it is credited as a courtesy on
the same basis as the Metro Transit and OVapi feeds. The feed publishes km/h,
so a new `speedUnit` registry field lets the proxy convert to m/s. Route ids
wrap the GTFS route id in an area prefix and are read as the line number.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

README.md

@@ -444,7 +444,7 @@ Twenty-one layers and map sources. **Nineteen have a keyless path.** Some offer
 | 📷 **Mapped ALPR Cameras**  | License-plate-reader camera locations tagged by OpenStreetMap contributors, loaded one city-sized view at a time, with **SHOW NEAREST**. Locations and tags only: no plate data, no video                                                                                                                                                                                           | OpenStreetMap (incl. DeFlock mapping)   | 🟢                                                                                                  |
 | 📷 **Street Level**         | Street-level photos behind one panel, one chip per provider: coverage on the streets, image cones, an embedded viewer with full-screen **EXPAND**. Mapillary, Google Street View, KartaView and Panoramax | Mapillary · Google · KartaView · Panoramax | 🟢 KartaView, Panoramax · 🟡 Mapillary token · 🔴 Google Maps key |
 | 📻 **Radio**                | Geolocated world radio with an **analog tuner** — drag the needle across up to 750 stations and the globe flies to each broadcaster                                                                                                                                                                                                                                                 | Radio Browser / broadcasters            | 🟢                                                                                                  |
-| 🚌 **Transit**              | Live buses, trams, metros, trains and ferries with delayed playback between reports, selected-vehicle trails, and mode-coloured DETECT labels — Boston, Austin, Minneapolis, Helsinki, the Netherlands, Norway, South East Queensland, Rio de Janeiro (buses and BRT), Szczecin, and nine in Ontario: Toronto (surface vehicles; the subway publishes no positions), Mississauga, Hamilton, Durham Region, York Region, Guelph, Burlington, Barrie and Kingston                                                                                                                                               | Operator GTFS-Realtime feeds            | 🟢                                                                                                  |
+| 🚌 **Transit**              | Live buses, trams, metros, trains and ferries with delayed playback between reports, selected-vehicle trails, and mode-coloured DETECT labels — Boston, Austin, Minneapolis, Helsinki, the Netherlands, Norway, South East Queensland, Rio de Janeiro (buses and BRT), Szczecin, Lisbon, and nine in Ontario: Toronto (surface vehicles; the subway publishes no positions), Mississauga, Hamilton, Durham Region, York Region, Guelph, Burlington, Barrie and Kingston                                                                                                                                               | Operator GTFS-Realtime feeds            | 🟢                                                                                                  |
 | 🚲 **Bikeshare**            | Live station availability                                                                                                                                                                                                                                                                                                                                                           | GBFS                                    | 🟢                                                                                                  |
 | 🧭 **Directions**           | Click A and B on the globe for a street-following drive, walk or cycle route draped on the terrain with turn-by-turn steps — then FLY the camera along it. No key, no geocoder, no mic                                                                                                                                                                                              | OSRM on FOSSGIS servers (OpenStreetMap) | 🟢                                                                                                  |
 | ⌖ **OSM Places**           | Voice place search ("hospitals in Kathmandu") from OpenStreetMap, drawn as numbered points that follow-up questions can filter. Needs your own Overpass server (`OVERPASS_UPSTREAMS`); off otherwise                                                                                                                                                                                                                                                                                                                               |