feat: renders drawpad, and saves files as epoch_uuid for better sorting on disk

.env.example

@@ -87,3 +87,15 @@
 # Custom HTML template file with {{title}}, {{form}}, {{entries}}, and {{style}} placeholders.
 # Uses built-in default if unset.
 # BOOK_TEMPLATE=./templates/default.html
+
+# Enable drawing canvas in submission form. Drawings are stored as PNG files in DATA_DIR/drawings/.
+# BOOK_ENABLE_DRAWINGS=false
+
+# Label for the drawing canvas.
+# BOOK_LABEL_DRAWING=Draw (optional):
+
+# Drawing canvas width in pixels.
+# BOOK_CANVAS_WIDTH=400
+
+# Drawing canvas height in pixels.
+# BOOK_CANVAS_HEIGHT=200