Add mileage tracking automation plan

https://claude.ai/code/session_015myTTMs6yDsAGarATe5ePZ

PLAN.md

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+# Mileage Tracking Automation — Plan
+
+## How it works
+
+1. Open the web app on your phone
+2. Take a photo of the odometer
+3. Claude Vision API reads the number automatically
+4. The km driven is calculated and saved to an Excel sheet
+5. Download the sheet anytime
+
+---
+
+## Stack
+
+| Layer       | Technology                  |
+|-------------|-----------------------------|
+| Backend     | Python + Flask              |
+| AI / OCR    | Claude API (vision)         |
+| Spreadsheet | openpyxl (Excel .xlsx)      |
+| Frontend    | Mobile-friendly HTML        |
+
+---
+
+## Excel sheet columns
+
+| Date       | Time  | Odometer (km) | Trip (km) | Notes |
+|------------|-------|---------------|-----------|-------|
+| 2026-03-18 | 08:14 | 84 320        | 47        | Work  |
+
+---
+
+## Files to create
+
+```
+Driverthing/
+├── app.py              # Flask server + Claude API call
+├── mileage.py          # Excel read/write logic
+├── templates/
+│   └── index.html      # Mobile camera upload page
+├── requirements.txt
+└── mileage_log.xlsx    # Generated, gitignored
+```
+
+---
+
+## Flow
+
+```
+Phone camera → upload photo
+    → Flask receives image
+        → Claude Vision: "What is the odometer reading?"
+            → Extract number
+                → Calculate delta from last reading
+                    → Append row to Excel
+                        → Show confirmation on screen
+```
+
+---
+
+## Implementation steps
+
+1. Set up Flask app with a file upload endpoint
+2. Send uploaded image to Claude API with a vision prompt
+3. Parse the odometer number from the response
+4. Read the last recorded odometer value from the Excel file
+5. Calculate the difference (km driven)
+6. Append a new row (date, time, odometer, trip km, notes) to the sheet
+7. Return confirmation to the browser
+8. Add a download button for the Excel file