chore: seal Design Vision v1 and monorepo scaffold

Archive the differentiated YuXinGu product docs, AI engineering system,
design contract, and Go/Vue scaffold. Next execution prioritizes Cece-parity
over early innovation (see .ai/product/STRATEGY.md).

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/api/internal/config/config.go

@@ -0,0 +1,27 @@
+// Package config loads process configuration from environment variables.
+package config
+
+import "os"
+
+// Config holds runtime settings for the API server.
+type Config struct {
+	HTTPAddr    string
+	DatabaseURL string
+	AppEnv      string
+}
+
+// Load reads configuration from the environment with safe defaults for local dev.
+func Load() Config {
+	return Config{
+		HTTPAddr:    getenv("HTTP_ADDR", ":8080"),
+		DatabaseURL: getenv("DATABASE_URL", "postgres://yuxingu:yuxingu@127.0.0.1:5432/yuxingu?sslmode=disable"),
+		AppEnv:      getenv("APP_ENV", "dev"),
+	}
+}
+
+func getenv(key, fallback string) string {
+	if v := os.Getenv(key); v != "" {
+		return v
+	}
+	return fallback
+}