DB optimization: pool, golang-migrate, consolidate to single Postgres

- Fix DB_NAME=db_yal -> mydb in api_yal .env
- Add connection pool (MaxOpenConns 25, MaxIdleConns 10, ConnMaxLifetime 30m)
- Replace GORM AutoMigrate with golang-migrate in api_yal and api_bb
- Create embedded SQL migrations for both APIs
- Add DB_SCHEMA support to api_bb config
- Consolidate to single Postgres: db_bb -> schema 'bb' on db container
- Remove db_bb service, bb-network, db_bb volume from compose
- Remove api_tp targets from Makefile
- Clean up old migrate.go

main_dc/BB/api_bb/internal/config/config.go

@@ -11,6 +11,7 @@ import (
 type Config struct {
 	Port        string
 	DatabaseURL string
+	DBSchema    string
 	StaticURL   string `env:"STATIC_URL" envDefault:"http://localhost:8080"`
 	JWTSecret   string `env:"JWT_SECRET,required"`
 
@@ -34,6 +35,7 @@ func Load() *Config {
 	return &Config{
 		Port:        port,
 		DatabaseURL: databaseURL,
+		DBSchema:    getEnv("DB_SCHEMA", "public"),
 		JWTSecret:   jwtSecret,
 	}
 }