feat: use AprilTag instead of QR code

APRILTAG_MIGRATION.md

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+# AprilTag Migration Summary
+
+## Completed Changes
+
+### 1. Database Migration ✅
+- Migrated from `qr_code` string field to `apriltag_id` integer field
+- Added constraint to ensure valid AprilTag IDs (0-586)
+- Created unique index for apriltag_id
+- Preserved old qr_code data as qr_code_old for rollback safety
+
+### 2. Schema Updates ✅
+- Updated `StorageLocation` schema to use `apriltag_id` instead of `qr_code`
+- Added validation for AprilTag ID range (0-586)
+- Implemented auto-assignment of next available ID
+- Added unique constraint validation
+
+### 3. Business Logic Refactoring ✅
+- Replaced `ComponentsElixir.QRCode` module with `ComponentsElixir.AprilTag` module
+- Updated inventory functions to use AprilTag IDs instead of QR code strings
+- Implemented AprilTag ID availability checking
+- Added bulk SVG generation functionality
+
+### 4. UI/UX Improvements ✅
+- Replaced dropdown with 587 options with better UX:
+  - Radio buttons for "Auto-assign" vs "Manual selection"
+  - Number input for specific ID selection when manual mode selected
+  - Shows available ID count and examples
+  - Different interface for add vs edit forms
+- Updated templates to show AprilTag information instead of QR codes
+- Added download functionality for AprilTag SVGs
+
+### 5. AprilTag Generation ✅
+- Created `ComponentsElixir.AprilTag` module for managing tag36h11 family
+- Generated all 587 placeholder SVG files with human-readable IDs
+- Added Mix task `mix apriltag.generate_all` for batch generation
+- SVG files served statically at `/apriltags/tag36h11_id_XXX.svg`
+
+### 6. Event Handling ✅
+- Updated LiveView event handlers for AprilTag scanning/assignment
+- Added mode switching for manual vs automatic assignment
+- Implemented proper form state management for different modes
+
+## Benefits Achieved
+
+1. **Better UX**: No more 587-option dropdown menu
+2. **Future-Ready**: AprilTags designed for multi-tag detection scenarios
+3. **Robust**: 587 unique IDs provide ample space without conflicts
+4. **Maintainable**: Simpler integer ID system vs complex string encoding
+5. **Industry Standard**: AprilTags widely used in robotics/AR applications
+
+## Current State
+
+- ✅ Database schema updated
+- ✅ All 587 placeholder SVG files generated
+- ✅ UI forms updated with better UX
+- ✅ Business logic migrated to AprilTag system
+- ⏳ **Next**: Real AprilTag pattern generation (future enhancement)
+- ⏳ **Next**: Camera detection integration (future enhancement)
+
+## Usage
+
+### Generate AprilTag SVGs
+```bash
+mix apriltag.generate_all           # Generate missing files
+mix apriltag.generate_all --force   # Regenerate all files
+```
+
+### Available AprilTag IDs
+- Range: 0-586 (tag36h11 family)
+- Auto-assignment picks next available ID
+- Manual assignment allows specific ID selection
+- Unique constraint prevents conflicts
+
+### File Locations
+- SVG files: `priv/static/apriltags/tag36h11_id_XXX.svg`
+- URL pattern: `/apriltags/tag36h11_id_XXX.svg`
+- Placeholder pattern includes human-readable ID label
+
+The system is now ready for use with AprilTags instead of QR codes! The placeholder SVGs will work perfectly for testing and development until we implement actual AprilTag pattern generation.