docs: add hero image to README

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

README.md

@@ -3,7 +3,13 @@
 
 # Immich Frame
 
-![PaperColor displaying a photo from Immich](docs/PaperColor.jpg)
+<p align="center">
+  <picture>
+    <img src="docs/PaperColor.jpg" alt="PaperColor displaying a photo from Immich" width="400" style="border-radius: 8px; box-shadow: 0 2px 8px rgba(0,0,0,0.15);">
+  </picture>
+  <br>
+  <sub>PaperColor showing a dithered photo with location and date metadata overlays</sub>
+</p>
 
 An ESP32 firmware for the [M5Stack PaperColor](https://shop.m5stack.com/products/m5paper-color-esp32s3-dev-kit) e-ink display that turns it into a digital photo frame powered by your [Immich](https://immich.app/) server.