docs: add application screenshots and interactive gallery

- Captured clean, full-page screenshots of all major application views
- Added an interactive HTML slide deck gallery for previewing features
- Created a high-resolution mosaic and a smaller preview mosaic
- Generated a Python script to automate mosaic creation
- Updated README.md with prominent links to the gallery and screenshots
- Added accessibility attributes (role="button", tabindex="0") to calendar rows

Made-with: Cursor

README.md

@@ -1,7 +1,17 @@
 # PI Weekly Newspaper
 
+[![Application Preview](docs/screenshots/mosaic_small.png)](docs/gallery.html)
+
 Generates weekly ePub "newspapers" from the [Plymouth Independent](https://www.plymouthindependent.org/) RSS feed, optimized for the Xtreink X4 e-reader (800x480 screen).
 
+[📸 View all screenshots](docs/screenshots.md) | [🖼️ View Interactive Gallery](docs/gallery.html)
+
+## Screenshots & Gallery
+
+- **[Interactive HTML Gallery](docs/gallery.html)** - A slide deck view of the app's features.
+- **[Markdown Screenshots List](docs/screenshots.md)** - A full page showing all screenshots with descriptions.
+- **[Large Mosaic](docs/screenshots/mosaic_large.png)** - A high-resolution 4x2 grid of all screenshots (great for sharing).
+
 ## Quick Start
 
 ```bash