refactor(api): restructured API for type safety, maintainability and docs generation

- These changes makes the API incombatible with previous versions
- Added new types for error handling, success responses, and health checks.
- Updated health check logic to utilize the new types for better clarity and structure.
- Refactored existing handlers to improve response consistency and error handling.
- Updated Makefile to include a new target for generating API types from Swagger.
- Updated "new agent" API to respond an encrypted cert pair

internal/utils/go.mod

@@ -1,6 +1,6 @@
 module github.com/yusing/go-proxy/internal/utils
 
-go 1.24.5
+go 1.25.0
 
 require (
 	github.com/goccy/go-yaml v1.18.0
@@ -8,7 +8,7 @@ require (
 	github.com/rs/zerolog v1.34.0
 	github.com/stretchr/testify v1.10.0
 	go.uber.org/atomic v1.11.0
-	golang.org/x/text v0.27.0
+	golang.org/x/text v0.28.0
 )
 
 require (
@@ -16,6 +16,6 @@ require (
 	github.com/mattn/go-colorable v0.1.14 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
 	github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 // indirect
-	golang.org/x/sys v0.34.0 // indirect
+	golang.org/x/sys v0.35.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )