Phase 0: project scaffold

- Go module + chi server with embedded SPA serving and /api/health
- internal/config env loader (local-dev defaults; auth/copyleaks deferred)
- React 19 + Vite 6 + Tailwind v4 frontend with full Petal design tokens
- Frontend embedded into the binary via web/embed.go (go:embed all:dist)
- README dev workflow, .env.example, BUILD_PLAN progress tracker
- Verified end-to-end: binary serves health, embedded SPA, and SPA fallback

internal/config/config.go

@@ -0,0 +1,63 @@
+package config
+
+import (
+	"os"
+	"time"
+)
+
+// Config holds all runtime configuration, loaded from environment variables.
+// See .env.example for the full list and defaults.
+type Config struct {
+	Port         string
+	BaseURL      string
+	DatabasePath string
+
+	// LLM
+	LLMBackend   string // "vllm" | "ollama"
+	LLMEndpoint  string
+	LLMModel     string // checkpoint model (small, fast)
+	LLMChatModel string // Ask Petal model; falls back to LLMModel if empty
+	LLMTimeout   time.Duration
+
+	// Auth (deferred — not wired in the local-dev build, kept for later)
+	AuthentikURL          string
+	AuthentikClientID     string
+	AuthentikClientSecret string
+	SessionSecret         string
+}
+
+// Load reads configuration from the environment, applying sane local-dev defaults.
+func Load() *Config {
+	return &Config{
+		Port:         env("PORT", "8080"),
+		BaseURL:      env("BASE_URL", "http://localhost:8080"),
+		DatabasePath: env("DATABASE_PATH", "./data/petal.db"),
+
+		LLMBackend:   env("LLM_BACKEND", "vllm"),
+		LLMEndpoint:  env("LLM_ENDPOINT", "http://localhost:8000"),
+		LLMModel:     env("LLM_MODEL", ""),
+		LLMChatModel: env("LLM_CHAT_MODEL", ""),
+		LLMTimeout:   envDuration("LLM_TIMEOUT", 30*time.Second),
+
+		AuthentikURL:          env("AUTHENTIK_URL", ""),
+		AuthentikClientID:     env("AUTHENTIK_CLIENT_ID", ""),
+		AuthentikClientSecret: env("AUTHENTIK_CLIENT_SECRET", ""),
+		SessionSecret:         env("SESSION_SECRET", "dev-insecure-secret-change-me"),
+	}
+}
+
+func env(key, fallback string) string {
+	if v := os.Getenv(key); v != "" {
+		return v
+	}
+	return fallback
+}
+
+func envDuration(key string, fallback time.Duration) time.Duration {
+	if v := os.Getenv(key); v != "" {
+		if d, err := time.ParseDuration(v); err == nil {
+			return d
+		}
+	}
+	return fallback
+}