feat(tests): add comprehensive unit, integration, and e2e tests for API and database functionality

- Implemented end-to-end tests for API health checks, performance, behavior, and documentation.
- Created integration tests for database connection, CRUD operations, transactions, and connection pool management.
- Developed unit tests for configuration loading, environment variable handling, validation, default values, and helper functions.
- Established a test setup with environment management and basic usage examples for the testing framework.

templates/project/.air.toml.raw

@@ -0,0 +1,40 @@
+# .air.toml - Air 热重载配置文件
+
+root = "."
+testdata_dir = "testdata"
+tmp_dir = "tmp"
+
+[build]
+  args_bin = []
+  bin = "./tmp/main"
+  cmd = "go build -o ./tmp/main ."
+  delay = 1000
+  exclude_dir = ["assets", "tmp", "vendor", "testdata", "frontend"]
+  exclude_file = []
+  exclude_regex = ["_test.go"]
+  exclude_unchanged = false
+  follow_symlink = false
+  full_bin = ""
+  include_dir = []
+  include_ext = ["go", "tpl", "tmpl", "html", "yaml", "yml", "toml"]
+  kill_delay = "0s"
+  log = "build-errors.log"
+  send_interrupt = false
+  stop_on_root = false
+
+[color]
+  app = ""
+  build = "yellow"
+  main = "magenta"
+  runner = "green"
+  watcher = "cyan"
+
+[log]
+  time = false
+
+[misc]
+  clean_on_exit = false
+
+[screen]
+  clear_on_rebuild = false
+  keep_scroll = true