Update documentation for item categories feature

- Add categories.json to file structure in both docs
- Document itemCategories loading in frontend architecture
- Add Item Categories section to README with category table
- Update data model to include category field
- Update filtering documentation with categoryFilter
- Add customization instructions for adding categories

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CLAUDE.md

@@ -13,6 +13,7 @@ Pantry is a simple web app for tracking kitchen pantry items. It's a single-page
 - `index.html` - Frontend (HTML/CSS/JS all in one file)
 - `api.php` - Backend API (JSON file-based storage)
 - `containers.json` - Container type definitions with categories
+- `categories.json` - Item category definitions (Flours, Spices, Pasta, etc.)
 - `og-image.png` - OpenGraph image for social sharing
 - `deploy` - Rsync deployment script
 
@@ -23,6 +24,7 @@ Pantry is a simple web app for tracking kitchen pantry items. It's a single-page
 - Uses QRCode.js from CDN for QR code generation
 - Custom CSS with CSS variables for theming (earthy color palette: cream, terracotta, forest green)
 - Container types loaded from `containers.json` at startup into `containerTypes` object
+- Item categories loaded from `categories.json` at startup into `itemCategories` object
 - All API calls go through the `apiCall()` function which POSTs to `api.php`
 
 **Backend (`api.php`)**:
@@ -36,6 +38,12 @@ Pantry is a simple web app for tracking kitchen pantry items. It's a single-page
 - Categories have: `name`, `containers[]`
 - Frontend displays as "Category: Container Name" (e.g., "Glass Spice Jars: Hex (Large)")
 
+**Item Categories (`categories.json`)**:
+- Defines item categories for organizing inventory (Flours, Spices, Pasta, Baking, etc.)
+- Each category has: key (e.g., `flours`), `name`, `color`
+- Category tabs are dynamically generated in the nav bar
+- Items display their category as a colored tag
+
 **Data Storage**:
 - `data/inventory.json` - Inventory items
 - `data/pin.txt` - 4-digit PIN for edit mode (plain text)
@@ -72,12 +80,13 @@ The `deploy` script uses rsync to push to YunoHost:
 ## Key Implementation Details
 
 **Data model:**
-- Items have: `id`, `name`, `container` (type ID), `outOfStock` (boolean)
+- Items have: `id`, `name`, `container` (type ID), `category` (category key), `outOfStock` (boolean)
 
 **Filtering:**
-- `currentFilter` - Tab filter: 'all', 'in-stock', 'out', 'spices', 'qr'
+- `currentFilter` - Tab filter: 'all', 'in-stock', 'out', 'category', 'recent', 'qr'
+- `categoryFilter` - Category filter (null or category key), set by clicking category tabs
 - `containerFilter` - Container type filter (null or container ID), set by clicking legend items
-- Both filters combine with search text
+- All filters combine with search text
 
 **Container legend:**
 - Clickable - filters inventory by that container type