Load .env.<APP_ENV>, validate config at boot, keep secrets out of the image

`main.go` only ever loaded `.env`; the `APP_ENV` switch described in
`.env.local` / `.env.production` did not exist, and a missing variable
surfaced one restart at a time as a log.Fatalf inside db.Connect.

config.Load now picks `.env.<APP_ENV>` (default local) then `.env`, with
real environment winning, reads every setting into one typed Config and
reports everything missing in one message. Production insists on a POS
signing secret; local warns when DB_HOST is not a local address. db,
redis and the image store take the Config instead of reading env
themselves.

Also:
- livehub read MQTT_USERNAME while everything else uses MQTT_USER, so the
  console stream connected to the broker unauthenticated. Both accepted.
- .dockerignore: `COPY . .` was baking .env.production into the image.
  Dockerfile sets APP_ENV=production.
- Drop utils/config.go (dead viper loader) and create_table.go (unused,
  hardcoded production DSN); go mod tidy removes viper.
- .env.example lists every variable the code reads; docs/ENVIRONMENT.md.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

db/connect.go

@@ -3,8 +3,8 @@ package db
 import (
 	"fmt"
 	"log"
+	"nearle/config"
 	"net/url"
-	"os"
 	"time"
 
 	"gorm.io/driver/postgres"
@@ -23,14 +23,18 @@ var (
 // DATABASE CONNECTION
 // --------------------
 
-func Connect() {
+// Connect opens the main database and then the optional catalogue database
+// and image store. Everything it needs has already been validated by
+// config.Load, so a missing variable can no longer surface here as a
+// log.Fatal halfway through boot.
+func Connect(cfg *config.Config) {
 	dsn := fmt.Sprintf(
 		"host=%s user=%s password=%s dbname=%s port=%s sslmode=disable TimeZone=Asia/Kolkata",
-		mustEnv("DB_HOST"),
-		mustEnv("DB_USER"),
-		mustEnv("DB_PASSWORD"),
-		mustEnv("DB_NAME"),
-		getEnv("DB_PORT", "5433"),
+		cfg.DB.Host,
+		cfg.DB.User,
+		cfg.DB.Password,
+		cfg.DB.Name,
+		cfg.DB.Port,
 	)
 
 	var err error
@@ -42,17 +46,16 @@ func Connect() {
 	setupDB(DB)
 	fmt.Println("✅ Database connected")
 
-	connectCatalogueDB()
-	connectImageStore()
+	connectCatalogueDB(cfg.Catalogue)
+	connectImageStore(cfg.S3)
 }
 
 // connectCatalogueDB opens the read-only connection to the catalogue
 // (pgvector) database. If its env vars are not set, catalogue endpoints
 // are simply unavailable — this must never block startup of the main app.
-func connectCatalogueDB() {
-	host := getEnv("CATALOGUE_DB_HOST", "")
-	if host == "" {
-		fmt.Println("⚠️  Catalogue DB env vars not set, skipping catalogue DB connection")
+func connectCatalogueDB(c config.DBConfig) {
+	if !c.Enabled() {
+		fmt.Println("⚠️  CATALOGUE_DB_HOST not set, skipping catalogue DB connection")
 		return
 	}
 
@@ -62,9 +65,9 @@ func connectCatalogueDB() {
 	// quoting/comment syntax.
 	dsnURL := url.URL{
 		Scheme: "postgres",
-		User:   url.UserPassword(mustEnv("CATALOGUE_DB_USER"), mustEnv("CATALOGUE_DB_PASSWORD")),
-		Host:   fmt.Sprintf("%s:%s", host, getEnv("CATALOGUE_DB_PORT", "5432")),
-		Path:   "/" + mustEnv("CATALOGUE_DB_NAME"),
+		User:   url.UserPassword(c.User, c.Password),
+		Host:   fmt.Sprintf("%s:%s", c.Host, c.Port),
+		Path:   "/" + c.Name,
 	}
 	q := dsnURL.Query()
 	q.Set("sslmode", "disable")
@@ -108,22 +111,3 @@ func CloseDB() {
 	}
 	fmt.Println("Connection closed Successfully")
 }
-
-// --------------------
-// ENV HELPERS
-// --------------------
-
-func mustEnv(key string) string {
-	val := os.Getenv(key)
-	if val == "" {
-		log.Fatalf("Missing required env variable: %s", key)
-	}
-	return val
-}
-
-func getEnv(key, fallback string) string {
-	if val := os.Getenv(key); val != "" {
-		return val
-	}
-	return fallback
-}