Fix WiFi file transfer crash by disabling WiFi sleep early

The previous commit added an initialization delay, but the device was still
crashing with a store access fault during web server operation. The root cause
was WiFi sleep mode causing instability in the ESP32 WiFi/TCP stack.

Root cause analysis:
- WiFi.setSleep(false) was only called when web server started
- By that time, WiFi operations had already occurred with sleep mode enabled
- WiFi sleep mode can cause memory corruption and crashes in the WiFi stack
- The crashes manifested as "Store access fault" errors during web server operation

Why hotspot-first workaround worked:
- Hotspot mode initialized WiFi and called setSleep(false) via web server
- This properly configured the WiFi hardware
- When switching to STA mode later, WiFi stack remained stable
- Direct STA mode start didn't have this initialization, causing crashes

Fix:
- Added WiFi.setSleep(false) immediately after WiFi.mode() in both STA and AP paths
- This disables sleep mode before any WiFi operations occur
- Prevents WiFi stack instability and memory corruption
- Matches the critical importance noted in CrossPointWebServer.cpp:54-55

Files changed:
- CrossPointWebServerActivity.cpp:142 - STA mode path
- CrossPointWebServerActivity.cpp:191 - AP mode path (for consistency)

src/activities/network/CrossPointWebServerActivity.cpp

@@ -139,6 +139,7 @@ void CrossPointWebServerActivity::onNetworkModeSelected(const NetworkMode mode)
     Serial.printf("[%lu] [WEBACT] Turning on WiFi (STA mode)...\n", millis());
     WiFi.mode(WIFI_STA);
     delay(100);  // Allow WiFi hardware to initialize before proceeding
+    WiFi.setSleep(false);  // Disable WiFi sleep immediately to prevent crashes
 
     state = WebServerActivityState::WIFI_SELECTION;
     Serial.printf("[%lu] [WEBACT] Launching WifiSelectionActivity...\n", millis());
@@ -187,6 +188,7 @@ void CrossPointWebServerActivity::startAccessPoint() {
   // Configure and start the AP
   WiFi.mode(WIFI_AP);
   delay(100);
+  WiFi.setSleep(false);  // Disable WiFi sleep immediately to prevent crashes
 
   // Start soft AP
   bool apStarted;