feat(bikeshare): add Barcelona's Bicing and AMBici

- Bicing (543 stations, PBSC) and AMBici (237 e-bike stations across the
  metropolitan area, nextbike) join the GBFS registry from the operators'
  keyless GBFS 2.3 feeds, both listed in MobilityData's systems catalogue.
- gbfs.nextbike.net joins the proxy allowlist as an exact host.
- Credits, DATA_SOURCES, CURRENT-STATE and CHANGELOG updated; a test pins
  each system's proxy reachability and the range check for its outermost
  stations.

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

DATA_SOURCES.md

@@ -68,6 +68,8 @@ How to read this:
 | **GBFS (Lyft / BCycle / Social Bicycles / PBSC)**                     | Bikeshare availability                                                                                                              | Per-feed (attribution-only)                                                                                                                                                                                                                                                                                                                           | Credit the operator (e.g. Austin BCycle) + its `license_url`                                                                                                   |
 | **Bike Share Toronto** (`toronto.publicbikesystem.net`) | Bikeshare station availability, Toronto | Operator GBFS feed. No licence is published: the City's open-data package declares none and the feed has no `license_url`. Attribution is given to the operator. | "Bike Share Toronto (Toronto Parking Authority)" |
 | **Bike Itaú (Tembici)** (`*.publicbikesystem.net`, seven Brazilian cities) | Bikeshare station availability: São Paulo, Rio de Janeiro, Salvador, Recife, Porto Alegre, Brasília and Curitiba | Operator GBFS feeds. No licence is published: the feeds' `system_information.json` carries no `license_url`, operator or attribution fields. Attribution is given to the operator. | "Bike Itaú (Tembici)" |
+| **Bicing** (`barcelona.publicbikesystem.net`) | Bikeshare station availability, Barcelona | Operator GBFS feed (PBSC), keyless. The feed publishes no licence; the City's own open-data copy of the same station data is CC BY 4.0 but needs a token. Attribution is given to the operator. | "Bicing, Barcelona City Council (B:SM)" |
+| **AMBici** (nextbike, `gbfs.nextbike.net`) | Bikeshare station availability, Barcelona metropolitan area (e-bikes) | Operator GBFS feed, keyless. `system_information.license_id` is **CC0-1.0**; no attribution required, given anyway. | "AMBici, Àrea Metropolitana de Barcelona, operated by nextbike" |
 | **Oslo / Bergen / Trondheim Bysykkel** (Urban Sharing, `gbfs.urbansharing.com`) | Bikeshare availability, Oslo, Bergen and Trondheim city bikes. Keyless GBFS; the proxy sends the `Client-Identifier` header the operators ask for | [NLOD 2.0](https://data.norge.no/nlod/en/2.0) — attribution REQUIRED ([Oslo](https://oslobysykkel.no/en/open-data/realtime), [Bergen](https://bergenbysykkel.no/en/apne-data/sanntid), [Trondheim](https://trondheimbysykkel.no/en/open-data/realtime)) | "Contains data under the Norwegian licence for Open Government data (NLOD) made available by Oslo Bysykkel, Bergen Bysykkel and Trondheim Bysykkel" |
 | **Kolumbus / Farte Bysykkel** (Entur Mobility, `api.entur.io/mobility/v2/gbfs`) | Bikeshare availability, Kolumbus Bysykkel (Stavanger/Nord-Jæren) and Farte Bysykkel (Skien/Porsgrunn). Keyless GBFS; the proxy sends the `ET-Client-Name` header Entur requires and is limited to Entur's GBFS paths | [NLOD](https://data.norge.no/nlod/en/2.0) per the [Entur Mobility API docs](https://developer.entur.org/pages-mobility-docs-mobility-v2) — attribution REQUIRED | "Contains data under the Norwegian licence for Open Government data (NLOD) made available by Entur (Kolumbus Bysykkel, Farte Bysykkel)" |
 | **JCDecaux Cyclocity** (`api.cyclocity.fr`) | Bikeshare availability, Bysykkel Lillestrøm. Keyless GBFS; the proxy is limited to JCDecaux contract paths | [Licence Ouverte / Etalab](https://developer.jcdecaux.com/files/Open-Licence-fr.pdf) (the feed's `license_url`) — attribution REQUIRED | "Bysykkel Lillestrøm: JCDecaux, Licence Ouverte" |