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

proto/rpc_create_user.proto

@@ -4,7 +4,7 @@ package pb;
 
 import "user.proto";
 
-option go_package = "github.com/FernandoJVideira/simple_bank/pb";
+option go_package = "github.com/FernandoJVideira/api_tmpl/pb";
 
 message CreateUserRequest {
     string username = 1;

proto/rpc_login_user.proto

@@ -5,7 +5,7 @@ package pb;
 import "user.proto";
 import "google/protobuf/timestamp.proto";
 
-option go_package = "github.com/FernandoJVideira/simple_bank/pb";
+option go_package = "github.com/FernandoJVideira/api_tmpl/pb";
 
 message LoginUserRequest {
     string username = 1;

proto/rpc_update_user.proto

@@ -4,7 +4,7 @@ package pb;
 
 import "user.proto";
 
-option go_package = "github.com/FernandoJVideira/simple_bank/pb";
+option go_package = "github.com/FernandoJVideira/api_tmpl/pb";
 
 message UpdateUserRequest {
     string username = 1;

proto/rpc_verify_email.proto

@@ -2,7 +2,7 @@ syntax = "proto3";
 
 package pb;
 
-option go_package = "github.com/FernandoJVideira/simple_bank/pb";
+option go_package = "github.com/FernandoJVideira/api_tmpl/pb";
 
 message VerifyEmailRequest {
     int64 id = 1;

proto/service_api_tmpl.proto

@@ -9,28 +9,28 @@ import "rpc_update_user.proto";
 import "rpc_verify_email.proto";
 import "protoc-gen-openapiv2/options/annotations.proto";
 
-option go_package = "github.com/FernandoJVideira/simple_bank/pb";
+option go_package = "github.com/FernandoJVideira/api_tmpl/pb";
 
 option (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_swagger) = {
   info: {
-    title: "Simple Bank API"
+    title: "API Template"
     version: "0.0.1"
     contact: {
       name: "fvideira"
-      url: "https://github.com/FernandoJVideira/simple_bank"
-      email: "03.pleaser-minster@icloud.com"
+      url: "https://github.com/FernandoJVideira/api_tmpl"
+      email: "support@example.com"
     };
   };
 };
 
-service SimpleBank {
+service ApiTmpl {
     rpc CreateUser (CreateUserRequest) returns (CreateUserResponse){
         option (google.api.http) = {
             post: "/v1/create_user"
             body: "*"
         };
         option (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_operation) = {
-              description: "Create a new user in the Simple Bank system."
+              description: "Create a new user."
               summary: "Create User"
         };
     }
@@ -40,7 +40,7 @@ service SimpleBank {
             body: "*"
         };
         option (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_operation) = {
-              description: "Login an existing user in the Simple Bank system."
+              description: "Login an existing user."
               summary: "Login User"
         };
     }
@@ -49,7 +49,7 @@ service SimpleBank {
             get: "/v1/verify_email"
         };
         option (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_operation) = {
-              description: "Verify user's email in the Simple Bank system."
+              description: "Verify a user's email."
               summary: "Verify Email"
         };
     }
@@ -59,7 +59,7 @@ service SimpleBank {
             body: "*"
         };
         option (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_operation) = {
-              description: "Update an existing user in the Simple Bank system."
+              description: "Update an existing user."
               summary: "Update User"
         };
     }

proto/user.proto

@@ -4,7 +4,7 @@ package pb;
 
 import "google/protobuf/timestamp.proto";
 
-option go_package = "github.com/FernandoJVideira/simple_bank/pb";
+option go_package = "github.com/FernandoJVideira/api_tmpl/pb";
 
 message User {
     string username = 1;