Add persistent cap catalog with image/name/color management

README.md

@@ -8,13 +8,17 @@ Prototype Flutter app for generating bottle-cap mosaics from imported images.
 - Resolution controls:
   - explicit grid width/height
   - or auto grid by approximate cap size in source image pixels
-- Cap palette management:
-  - list caps with name + color
-  - add color via picker and/or manual hex
-  - **Deckel fotografieren**: capture a cap with camera and auto-detect its color from a robust center-circle sample (reduced background contamination)
-  - review detected color preview, edit name + hex, then save as a normal palette entry
-  - remove caps
+- Persistent **Cap Catalog** (local JSON in app documents directory):
+  - each entry stores `name`, `color` (hex/swatch), and optional preview image path
+  - survives app restarts
+- Catalog management:
+  - add entries manually (name + hex/color picker + optional photo)
+  - **Deckel fotografieren**: capture a cap with camera, auto-detect dominant center color, store cropped thumbnail
+  - dedicated catalog browser with **list/grid** modes
+  - edit existing entry name/color
+  - delete entries (with thumbnail cleanup)
 - Mosaic preview + bill of materials counts per cap color
+- Mosaic palette source is always the current catalog entries
 
 ## Style controls (new)