chore(restructure): reorganize project layout

- Reorganize internal packages and overall project structure
- Update imports and wiring to match the new layout
- Separate HTTP parsing and streaming from the server package
- Separate middleware from the server package
- Separate session registry from the session package
- Move HTTP, HTTPS, and TCP servers to the transport package
- Session package no longer starts the TCP server directly
- Server package no longer starts HTTP/HTTPS servers on initialization
- Forwarder no longer handles accepting TCP requests
- Move session details to the types package
- HTTP/HTTPS initialization is now the responsibility of main

internal/middleware/middleware.go

@@ -0,0 +1,13 @@
+package middleware
+
+import (
+	"tunnel_pls/internal/http/header"
+)
+
+type RequestMiddleware interface {
+	HandleRequest(header header.RequestHeader) error
+}
+
+type ResponseMiddleware interface {
+	HandleResponse(header header.ResponseHeader, body []byte) error
+}