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/config/config.go

@@ -0,0 +1,88 @@
+// Package config loads workout-suggester settings from the environment and
+// an optional .env file.
+package config
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strings"
+	"time"
+)
+
+// Config holds all runtime settings.
+type Config struct {
+	Addr         string        // ADDR: where the web UI listens
+	BaseURL      string        // LLM_BASE_URL: OpenAI-compatible API root, e.g. http://127.0.0.1:8000/v1
+	APIKey       string        // LLM_API_KEY: optional bearer token for the model server
+	Model        string        // LLM_MODEL: model id; empty means "first model the server lists"
+	Timeout      time.Duration // LLM_TIMEOUT: upper bound for a single reply
+	OverpassURL  string        // OVERPASS_URL: OpenStreetMap Overpass API endpoint
+	BRouterURL   string        // BROUTER_URL: BRouter endpoint for loops from your door; "-" disables
+	DefaultPlace string        // DEFAULT_PLACE: prefilled town in the form
+	ForecastURL  string        // OPEN_METEO_URL: forecast endpoint (Open-Meteo is self-hostable)
+	GeocodeURL   string        // OPEN_METEO_GEOCODE_URL: place search endpoint
+}
+
+// Load reads the configuration from environment variables, applying defaults.
+func Load() (Config, error) {
+	c := Config{
+		Addr:         env("ADDR", "127.0.0.1:3000"),
+		BaseURL:      strings.TrimRight(env("LLM_BASE_URL", "http://127.0.0.1:8000/v1"), "/"),
+		APIKey:       os.Getenv("LLM_API_KEY"),
+		Model:        os.Getenv("LLM_MODEL"),
+		Timeout:      3 * time.Minute,
+		OverpassURL:  env("OVERPASS_URL", "https://overpass-api.de/api/interpreter"),
+		BRouterURL:   env("BROUTER_URL", "https://brouter.de/brouter"),
+		DefaultPlace: os.Getenv("DEFAULT_PLACE"),
+		ForecastURL:  env("OPEN_METEO_URL", "https://api.open-meteo.com/v1/forecast"),
+		GeocodeURL:   env("OPEN_METEO_GEOCODE_URL", "https://geocoding-api.open-meteo.com/v1/search"),
+	}
+	if v := os.Getenv("LLM_TIMEOUT"); v != "" {
+		d, err := time.ParseDuration(v)
+		if err != nil {
+			return c, fmt.Errorf("LLM_TIMEOUT: %w", err)
+		}
+		c.Timeout = d
+	}
+	return c, nil
+}
+
+func env(key, fallback string) string {
+	if v, ok := os.LookupEnv(key); ok && v != "" {
+		return v
+	}
+	return fallback
+}
+
+// LoadEnvFile sets variables from a KEY=VALUE file. Variables that are
+// already set in the environment win, so the real environment can override
+// the file. Blank lines and lines starting with # are ignored; values may be
+// wrapped in single or double quotes.
+func LoadEnvFile(path string) error {
+	f, err := os.Open(path)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	sc := bufio.NewScanner(f)
+	for n := 1; sc.Scan(); n++ {
+		line := strings.TrimSpace(sc.Text())
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+		key, val, ok := strings.Cut(strings.TrimPrefix(line, "export "), "=")
+		if !ok {
+			return fmt.Errorf("%s:%d: expected KEY=VALUE", path, n)
+		}
+		key, val = strings.TrimSpace(key), strings.TrimSpace(val)
+		if len(val) >= 2 && (val[0] == '"' || val[0] == '\'') && val[len(val)-1] == val[0] {
+			val = val[1 : len(val)-1]
+		}
+		if _, set := os.LookupEnv(key); !set {
+			os.Setenv(key, val)
+		}
+	}
+	return sc.Err()
+}