docs: add per package README for implementation details (AI generated with human review)

internal/net/gphttp/README.md

@@ -0,0 +1,146 @@
+# gphttp
+
+HTTP utilities package providing transport configuration, default HTTP client, and a wrapper around `http.ServeMux` with panic recovery.
+
+## Overview
+
+This package provides shared HTTP utilities used throughout GoDoxy:
+
+- **Default HTTP Client**: Pre-configured `http.Client` with secure settings
+- **Transport Factory**: Functions to create optimized `http.Transport` configurations
+- **ServeMux Wrapper**: Extended `http.ServeMux` with panic recovery for handler registration
+
+## Architecture
+
+```mermaid
+graph TD
+    A[HTTP Request] --> B[gphttp.Client]
+    B --> C[Transport]
+    C --> D[Network Connection]
+
+    E[Server Setup] --> F[gphttp.ServeMux]
+    F --> G[http.ServeMux]
+    G --> H[HTTP Handlers]
+```
+
+## Core Components
+
+### HTTP Client
+
+The package exports a pre-configured `http.Client` with secure defaults:
+
+```go
+var (
+    httpClient = &http.Client{
+        Timeout: 5 * time.Second,
+        Transport: &http.Transport{
+            DisableKeepAlives: true,
+            ForceAttemptHTTP2: false,
+            DialContext: (&net.Dialer{
+                Timeout:   3 * time.Second,
+                KeepAlive: 60 * time.Second,
+            }).DialContext,
+            TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
+        },
+    }
+
+    Get  = httpClient.Get
+    Post = httpClient.Post
+    Head = httpClient.Head
+    Do   = httpClient.Do
+)
+```
+
+### Transport Factory
+
+Functions for creating optimized HTTP transports:
+
+```go
+// NewTransport creates an http.Transport with proxy support and optimized settings
+func NewTransport() *http.Transport
+
+// NewTransportWithTLSConfig creates an http.Transport with custom TLS configuration
+func NewTransportWithTLSConfig(tlsConfig *tls.Config) *http.Transport
+```
+
+Default transport settings:
+
+- `MaxIdleConnsPerHost`: 1000
+- `IdleConnTimeout`: 90 seconds
+- `TLSHandshakeTimeout`: 10 seconds
+- `ResponseHeaderTimeout`: 60 seconds
+- `WriteBufferSize` / `ReadBufferSize`: 16KB
+
+### ServeMux Wrapper
+
+Extended `http.ServeMux` with panic recovery:
+
+```go
+type ServeMux struct {
+    *http.ServeMux
+}
+
+func NewServeMux() ServeMux
+func (mux ServeMux) Handle(pattern string, handler http.Handler) (err error)
+func (mux ServeMux) HandleFunc(pattern string, handler http.HandlerFunc) (err error)
+```
+
+The `Handle` and `HandleFunc` methods recover from panics and return them as errors, preventing one bad handler from crashing the entire server.
+
+## Usage Examples
+
+### Using the Default Client
+
+```go
+import "github.com/yusing/godoxy/internal/net/gphttp"
+
+// Simple GET request
+resp, err := gphttp.Get("https://example.com")
+if err != nil {
+    log.Fatal(err)
+}
+defer resp.Body.Close()
+
+// POST request
+resp, err := gphttp.Post("https://example.com", "application/json", body)
+```
+
+### Creating Custom Transports
+
+```go
+import (
+    "crypto/tls"
+    "net/http"
+    "github.com/yusing/godoxy/internal/net/gphttp"
+)
+
+// Default transport with environment proxy
+transport := gphttp.NewTransport()
+
+// Custom TLS configuration
+tlsConfig := &tls.Config{
+    ServerName: "example.com",
+}
+transport := gphttp.NewTransportWithTLSConfig(tlsConfig)
+```
+
+### Using ServeMux with Panic Recovery
+
+```go
+mux := gphttp.NewServeMux()
+
+// Register handlers - panics are converted to errors
+if err := mux.HandleFunc("/api", apiHandler); err != nil {
+    log.Printf("handler registration failed: %v", err)
+}
+```
+
+## Integration Points
+
+- Used by `internal/net/gphttp/middleware` for HTTP request/response processing
+- Used by `internal/net/gphttp/loadbalancer` for backend connections
+- Used throughout the route handling system
+
+## Configuration
+
+The default client disables HTTP/2 (`ForceAttemptHTTP2: false`) and keep-alives (`DisableKeepAlives: true`) for security and compatibility reasons. The transport uses environment proxy settings via `http.ProxyFromEnvironment`.