Rename geotargeting to georouting and simplify to per-region edge hosts

[etiennelatendresse-optable]

Follow-up to the merged geotargeting addon

What changed

• Rename geotargetingto georouting
• All regions use their edge host: US -> na.edge, CA -> ca.edge, EU -> eu.edge, AU -> au.edge
• Dropped the -auth handling and the tuple GeoMapEntry moving toward one tenant/DCN per customer per region. GeoMap is now a plain Record<string, string> (geo -> host).
• getGeoRouting(geo, geoMap?) returns the host string or null, instead of getGeoConfig(nodeName, geo) returning { host, node }. The caller supplies node/site, this addon only resolves the host.

Open decision regarding US/CA on the same edge

The simplification now only returns the host. That cleanly handles the common case (each region has its own edge host), but if a customer runs separate US and CA DCNs on the same edge (e.g. both on na.edge), the host alone can't differentiate them, the caller must pick the DCN via node/site, or pass a custom GeoMap. This is documented in the README and the module header.

How to test

• Tested
• Docs / README updated

[mosherBT]

Don't merge until @jplaroche reviews

[jplaroche]

LGTM