📒 docs: improve clarity for ProxyHeader and TrustProxy configuration

docs/api/ctx.md

@@ -1145,14 +1145,45 @@ app.Get("/", func(c fiber.Ctx) error {
 })
 ```
 
-When registering the proxy request header in the Fiber app, the IP address of the header is returned [(Fiber configuration)](fiber.md#proxyheader)
+:::info
+By default, `c.IP()` returns the remote IP address from the TCP connection. When your Fiber app is behind a reverse proxy (like Nginx, Traefik, or a load balancer), you need to configure **both** [`TrustProxy`](fiber.md#trustproxy) and [`ProxyHeader`](fiber.md#proxyheader) to read the client IP from proxy headers like `X-Forwarded-For`.
 
-```go
+**Important:** You must enable `TrustProxy` and configure trusted proxy IPs to prevent header spoofing. Simply setting `ProxyHeader` alone will not work.
+
+**Note:** When using a proxy header such as `X-Forwarded-For`, `c.IP()` returns the raw header value unless [`EnableIPValidation`](fiber.md#enableipvalidation) is enabled. For `X-Forwarded-For`, this raw value may be a comma-separated list of IPs; enable `EnableIPValidation` if you need `c.IP()` to return a single, validated client IP.
+:::
+
+#### Configuration for apps behind a reverse proxy
+
+```go title="Example - Basic Configuration"
+app := fiber.New(fiber.Config{
+  // Enable proxy support
+  TrustProxy: true,
+  // Specify which header contains the real client IP
+  ProxyHeader: fiber.HeaderXForwardedFor,
+  // Configure which proxy IPs to trust
+  TrustProxyConfig: fiber.TrustProxyConfig{
+    // Trust private IP ranges (for internal load balancers)
+    Private: true,
+    // Or specify exact proxy IPs/ranges
+    // Proxies: []string{"10.10.0.58", "192.168.0.0/24"},
+  },
+})
+```
+
+```go title="Example - Specific Proxy IPs"
 app := fiber.New(fiber.Config{
+  TrustProxy: true,
   ProxyHeader: fiber.HeaderXForwardedFor,
+  TrustProxyConfig: fiber.TrustProxyConfig{
+    // Trust only specific proxy IP addresses
+    Proxies: []string{"10.10.0.58", "192.168.1.0/24"},
+  },
 })
 ```
 
+See [`TrustProxy`](fiber.md#trustproxy) and [`TrustProxyConfig`](fiber.md#trustproxyconfig) for more details on security considerations and configuration options.
+
 ### IPs
 
 Returns an array of IP addresses specified in the [X-Forwarded-For](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Forwarded-For) request header.