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/version/version.go

@@ -0,0 +1,17 @@
+package version
+
+import "fmt"
+
+var (
+	Version   = "dev"
+	BuildDate = "unknown"
+	Commit    = "unknown"
+)
+
+func GetVersion() string {
+	return fmt.Sprintf("tunnel_pls %s (commit: %s, built: %s)", Version, Commit, BuildDate)
+}
+
+func GetShortVersion() string {
+	return Version
+}