improve: clarify rotation detection in AI extraction prompt

- Emphasize MEASURING TEXT ANGLE precisely, not item orientation
- Add explicit calibration examples (22°, 90°, -45°, etc.)
- Clarify positive = counter-clockwise, negative = clockwise
- Help AI understand baseline measurement concept
- Keep all field identification rules unchanged

config/ai_prompt.md

@@ -90,14 +90,26 @@
     - Include minimal padding (10-15 pixels) around item edges
     - Ignore background clutter, other items, hands, reflections
 
-  ### Rotation Analysis
-  - Check if item labels/text are readable
-  - If text is rotated (not horizontal), calculate rotation needed
-  - Return `rotation_degrees`: degrees to rotate CLOCKWISE to make text readable
-  - Examples:
-    - Text rotated 90° counter-clockwise → return 90 (rotate 90° clockwise)
-    - Text rotated 45° clockwise → return -45 (rotate 45° counter-clockwise)
-    - Text already readable → return 0
+  ### Rotation Analysis (CRITICAL - MEASURE TEXT ANGLE)
+  
+  **PRIORITY: Measure text orientation, not item orientation**
+  
+  1. **Locate readable text** on the item (part numbers, manufacturer names, specifications, labels)
+  2. **Measure the baseline angle of that text**:
+     - Baseline = the invisible line the text sits on
+     - 0° = text baseline is HORIZONTAL (readable left-to-right)
+     - Positive degrees = text rotated counter-clockwise from horizontal
+     - Negative degrees = text rotated clockwise from horizontal
+  3. **Return clockwise rotation needed to make text horizontal**:
+     - If text tilted 22° counter-clockwise → return `+22` (rotate 22° clockwise to fix)
+     - If text tilted 15° clockwise → return `-15` (rotate 15° counter-clockwise to fix)
+     - If text already horizontal → return `0`
+  4. **Calibration examples** (measure the text angle precisely):
+     - Text reads perfectly left-to-right → `rotation_degrees: 0`
+     - Text tilted counter-clockwise, needs ~22° clockwise to straighten → `rotation_degrees: 22`
+     - Text vertical, pointing left (rotated 90° counter-clockwise) → `rotation_degrees: 90`
+     - Text vertical, pointing right (rotated 90° clockwise) → `rotation_degrees: -90`
+     - Text tilted clockwise by ~45° → `rotation_degrees: -45`
 
   ### Confidence Score
   - Return `confidence`: 0.0-1.0 indicating reliability of crop/rotation analysis