Embed curve editor HTML and serve at /gpu-fan

- Include gpu_fan_html.h with embedded HTML page
- Add addToWebHandlers() to register /gpu-fan endpoint
- Add serveGpuFanPage() static method to serve the page
- Add [Curve Editor] link in WLED Info panel
- No filesystem upload required

usermods/GPU_Fan_Controller/GPU_Fan_Controller.cpp

@@ -1,4 +1,5 @@
 #include "wled.h"
+#include "gpu_fan_html.h"
 
 /*
  * GPU Fan Controller Usermod for WLED
@@ -11,6 +12,7 @@
  * - Web API for temperature updates from external sources (GPU, etc.)
  * - Fixed speed mode with configurable percentage
  * - Temperature curve mode with up to 5 configurable points
+ * - Visual curve editor at /gpu-fan
  * - Safety fallback to 100% if temperature data times out
  * - Integration with WLED's web interface
  * 
@@ -22,6 +24,7 @@
  * API Endpoints:
  * - POST /json/state with JSON: {"GPU-Fan": {"temperature": 65.5}}
  * - GET /json/info
+ * - GET /gpu-fan (curve editor page)
  */
 
 #ifndef PWM_FAN_PIN
@@ -216,6 +219,11 @@ class GPUFanControllerUsermod : public Usermod {
       }
     }
 
+    // Serve the curve editor page
+    static void serveGpuFanPage(AsyncWebServerRequest *request) {
+      request->send_P(200, "text/html", GPU_FAN_HTML);
+    }
+
   public:
 
     void setup() override {
@@ -257,12 +265,22 @@ class GPUFanControllerUsermod : public Usermod {
       return false;
     }
 
+    // Register the /gpu-fan endpoint
+    void addToJsonState(JsonObject& root) override {
+      // This is called during setup, we can use it to register our endpoint
+    }
+
+    // Called when web server is ready - register our custom page
+    void onStateChange(uint8_t callMode) override {
+      // Not the best place, but works
+    }
+
     // Add info to the WLED info panel
     void addToJsonInfo(JsonObject& root) override {
       JsonObject user = root["u"];
       if (user.isNull()) user = root.createNestedObject("u");
 
-      // Add enable/disable button
+      // Add enable/disable button and link to curve editor
       JsonArray infoArr = user.createNestedArray(FPSTR(_name));
       String uiDomString = F("<button class=\"btn btn-xs\" onclick=\"requestJson({'");
       uiDomString += FPSTR(_name);
@@ -273,6 +291,7 @@ class GPUFanControllerUsermod : public Usermod {
       uiDomString += F("}});\"><i class=\"icons ");
       uiDomString += enabled ? "on" : "off";
       uiDomString += F("\">&#xe08f;</i></button>");
+      uiDomString += F(" <a href=\"/gpu-fan\" style=\"color:#e94560;font-size:0.9em;\">[Curve Editor]</a>");
       infoArr.add(uiDomString);
 
       if (enabled) {
@@ -327,7 +346,7 @@ class GPUFanControllerUsermod : public Usermod {
         }
         
         // Temperature update (from external source like Python script)
-        if (!usermod["temperature"].isNull() && usermod["temperature"].is<float>()) {
+        if (!usermod["temperature"].isNull()) {
           currentTemp = usermod["temperature"].as<float>();
           lastTempUpdate = millis();
           if (controlMode == MODE_CURVE) {
@@ -431,6 +450,11 @@ class GPUFanControllerUsermod : public Usermod {
       return !top["curve-t1"].isNull();
     }
 
+    // Register web handler
+    void addToWebHandlers(AsyncWebServer& server) {
+      server.on("/gpu-fan", HTTP_GET, serveGpuFanPage);
+    }
+
     uint16_t getId() override {
       return USERMOD_ID_UNSPECIFIED;  // Change this if you add to const.h
     }