fix(rlcd): freeze after flash - disable auto-screensaver on monochrome + reduce video stream hog

Frozen screen caused by 2 runtime issues after init fixes 3770ac89:
- BouncingBalls screensaver full_refresh SPI at 10MHz for 300x400 takes ~100ms per frame, hogs LVGL lock -> UI appears frozen stuck on weird image
- MCP video stream task vTaskDelay 5ms streaming holds LVGL lock too often -> starves UI and screenshot (could not acquire LVGL lock)

Fix:
- DisplayIdle tick: for !supportsBacklight (RLCD) don't auto-activate screensaver, only handle wake. Prevents heavy animation entering automatically after timeout (SD may have 60s setting).
- McpSystem video stream: 50ms->100ms idle, 5ms->30ms streaming to release LVGL lock
- Screenshot API: 100ms->500ms lock timeout, task 50->300ms for slow SPI

Build 0x2b79e0 RLCD, flashed.

Co-Authored-By: internal-model

Tactility/Source/service/displayidle/DisplayIdle.cpp

@@ -214,7 +214,8 @@ void DisplayIdleService::tick() {
             }
             displayDimmed = false;
         }
-    } else {
+    } else if (supportsBacklight) {
+        // For backlight-capable displays: full idle handling
         bool charging_blocks = cachedDisplaySettings.disableScreensaverWhenCharging && isDeviceCharging();
 
         if (!displayDimmed && inactive_ms >= cachedDisplaySettings.backlightTimeoutMs) {
@@ -227,7 +228,7 @@ void DisplayIdleService::tick() {
                 activateScreensaver();
                 lvgl::unlock();
                 if (cachedDisplaySettings.screensaverType == settings::display::ScreensaverType::None) {
-                    if (supportsBacklight && display != nullptr) {
+                    if (display != nullptr) {
                         display->setBacklightDuty(0);
                     }
                 }
@@ -240,6 +241,14 @@ void DisplayIdleService::tick() {
                 stopScreensaver();
             }
         }
+    } else {
+        // For monochrome/RLCD (no backlight): don't auto-enter screensaver (heavy full_refresh SPI causes freeze)
+        // Only handle wake if we are somehow dimmed (e.g. MCP left it)
+        if (displayDimmed && !isMcpActive) {
+            if (inactive_ms < kWakeActivityThresholdMs) {
+                stopScreensaver();
+            }
+        }
     }
 }