feat: metadata overlay tweaks — location badge, rounded corners, translucent option

- Location gets its own badge in the lower-left corner (separate from
  the main date/time/people/camera badge at the configured position)
- All overlay badges now use rounded corners (radius 4px) via
  fillRoundRect instead of fillRect
- New setting: 'Translucent background?' checkbox in web UI
  When enabled, badge backgrounds use a checkerboard pattern (every
  other pixel black) instead of solid black, creating a 50% opacity
  effect that lets the underlying image show through
- Refactored all badge drawing through a single drawOverlayBadge()
  helper (metadata, sleep indicator, battery indicator)

Co-authored-by: Cursor <cursoragent@cursor.com>

src/main.cpp

@@ -63,6 +63,7 @@ void displayTask(void* param) {
         Settings s = settingsManager.get();
         imagePipeline.setPipelineMode(static_cast<PipelineMode>(s.pipeline_mode));
         imagePipeline.setBlueNoiseEnabled(s.dither_noise != 0);
+        displayManager.setTranslucent(s.meta_translucent != 0);
         unsigned long intervalMs = s.interval_min * 60000UL;
 
         bool shouldRefresh = false;
@@ -246,10 +247,11 @@ void timerWakeCycle() {
         return;
     }
 
-    // Initialize Immich client and apply pipeline mode
+    // Initialize Immich client and apply pipeline/display modes
     immichClient.begin(s.immich_url, s.immich_key);
     imagePipeline.setPipelineMode(static_cast<PipelineMode>(s.pipeline_mode));
     imagePipeline.setBlueNoiseEnabled(s.dither_noise != 0);
+    displayManager.setTranslucent(s.meta_translucent != 0);
 
     // Fetch a small batch of random assets
     static constexpr int TIMER_WAKE_RETRIES = 5;