feat: workout-suggester, weather-aware workouts from a local Gemma

Go + Templ + HTMX app that checks the weather (Open-Meteo, MET Norway
fallback), scores run/ride/walk with plain rules, and has a local
open-weight model (Gemma 4 E2B via any OpenAI-compatible server) write
the plan. Routes are loops from your door (BRouter) plus signposted
OpenStreetMap routes (Overpass), with GPX export.

internal/weather/testdata/nominatim.json

@@ -0,0 +1 @@
+[{"place_id":101749274,"licence":"Data © OpenStreetMap contributors, ODbL 1.0. http://osm.org/copyright","osm_type":"relation","osm_id":897671,"lat":"51.0538286","lon":"3.7250121","category":"boundary","type":"administrative","place_rank":14,"importance":0.6930824855023677,"addresstype":"city","name":"Ghent","display_name":"Ghent, Gent, East Flanders, Flanders, Belgium","boundingbox":["50.9795422","51.1888910","3.5797616","3.8493413"]}]