chore: rename simple_bank to api_tmpl and clean up for template use

Rename the module, proto service, and all identifiers from simple_bank/
SimpleBank to api_tmpl/ApiTmpl, and regenerate the gRPC/gateway/swagger/
mock code accordingly.

- Scrub real secrets (SMTP password, auth token secret) from api.env/
  api_test.env, untrack them, and add api.env.example/api_test.env.example
- Remove committed build artifacts (tmp/main, tmp/build-errors.log,
  dbml-error.log) and gitignore them going forward
- Fix Dockerfile paths (build target, migrations copy) that referenced a
  stale project layout
- Rewrite README to match the actual cmd/ + internal/ structure and add a
  "using this as a template" section

cmd/api/main.go

@@ -15,15 +15,15 @@ import (
 	"github.com/rs/zerolog/log"
 	"golang.org/x/sync/errgroup"
 
-	"github.com/FernandoJVideira/simple_bank/internal/auth"
-	"github.com/FernandoJVideira/simple_bank/internal/config"
-	db "github.com/FernandoJVideira/simple_bank/internal/db/sqlc"
-	gapi "github.com/FernandoJVideira/simple_bank/internal/handlers/grpc"
-	api "github.com/FernandoJVideira/simple_bank/internal/handlers/http"
-	"github.com/FernandoJVideira/simple_bank/internal/mailer"
-	"github.com/FernandoJVideira/simple_bank/internal/service"
-	"github.com/FernandoJVideira/simple_bank/internal/worker"
-	"github.com/FernandoJVideira/simple_bank/pb"
+	"github.com/FernandoJVideira/api_tmpl/internal/auth"
+	"github.com/FernandoJVideira/api_tmpl/internal/config"
+	db "github.com/FernandoJVideira/api_tmpl/internal/db/sqlc"
+	gapi "github.com/FernandoJVideira/api_tmpl/internal/handlers/grpc"
+	api "github.com/FernandoJVideira/api_tmpl/internal/handlers/http"
+	"github.com/FernandoJVideira/api_tmpl/internal/mailer"
+	"github.com/FernandoJVideira/api_tmpl/internal/service"
+	"github.com/FernandoJVideira/api_tmpl/internal/worker"
+	"github.com/FernandoJVideira/api_tmpl/pb"
 
 	"github.com/golang-migrate/migrate/v4"
 	_ "github.com/golang-migrate/migrate/v4/database/postgres"
@@ -36,7 +36,7 @@ import (
 	"google.golang.org/grpc/reflection"
 	"google.golang.org/protobuf/encoding/protojson"
 
-	_ "github.com/FernandoJVideira/simple_bank/docs/statik"
+	_ "github.com/FernandoJVideira/api_tmpl/docs/statik"
 )
 
 var interruptSignals = []os.Signal{
@@ -45,13 +45,13 @@ var interruptSignals = []os.Signal{
 	syscall.SIGINT,
 }
 
-// @title Simple Bank API
+// @title API Template
 // @version 1.0
-// @description API for Simple Bank application
+// @description Backend API template service
 // @termsOfService http://swagger.io/terms/
 
 // @contact.name API Support
-// @contact.email support@simplebank.com
+// @contact.email support@example.com
 
 // @license.name MIT
 // @license.url https://opensource.org/licenses/MIT
@@ -181,7 +181,7 @@ func runGrpcServer(ctx context.Context, wg *errgroup.Group, config config.Config
 	grpcLogger := grpc.UnaryInterceptor(gapi.GrpcLogger)
 
 	grpcServer := grpc.NewServer(grpcLogger)
-	pb.RegisterSimpleBankServer(grpcServer, server)
+	pb.RegisterApiTmplServer(grpcServer, server)
 	reflection.Register(grpcServer)
 
 	listener, err := net.Listen("tcp", config.GrpcServerAddr)
@@ -228,7 +228,7 @@ func runGatewayServer(ctx context.Context, wg *errgroup.Group, config config.Con
 
 	grpcMux := runtime.NewServeMux(opts)
 
-	err = pb.RegisterSimpleBankHandlerServer(ctx, grpcMux, server)
+	err = pb.RegisterApiTmplHandlerServer(ctx, grpcMux, server)
 	if err != nil {
 		log.Fatal().Err(err).Msg("cannot register handler server")
 	}