feat(bikeshare): add Oslo, Bergen and Trondheim Bysykkel

Add Norway's three Urban Sharing city-bike systems to the Bike Share
layer and get_bike_share. The feeds are keyless GBFS on
gbfs.urbansharing.com, which joins the proxy allowlist. The proxy now
sends the Client-Identifier header the operators ask clients to send.
Attributed under NLOD 2.0 in DATA_SOURCES.md and the data credits.

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

server/providers/gbfs.js

@@ -11,6 +11,9 @@ import {
 /** Upstream fetch timeout for GBFS requests (ms). */
 const GBFS_PROXY_TIMEOUT_MS = 12000;
 
+/** Value of the Client-Identifier header sent with every upstream request. */
+export const GBFS_CLIENT_IDENTIFIER = 'gods-eye-view';
+
 export const GBFS_MAX_BODY_BYTES = 5 * 1024 * 1024; // 5 MB
 
 function gbfsRedirectHost(location, requestUrl) {
@@ -60,6 +63,9 @@ export async function fetchGbfsUpstream(
       headers: {
         Accept: 'application/json',
         'User-Agent': 'gods-eye-view-gbfs-proxy/1.0',
+        // Urban Sharing (the Norwegian city-bike feeds) asks every client to
+        // name itself in this header; other operators ignore it.
+        'Client-Identifier': GBFS_CLIENT_IDENTIFIER,
       },
       redirect: 'manual',
       signal: controller.signal,