Update README with correct dashboard run command

README.md

@@ -30,10 +30,12 @@ This project implements a flexible, modular dashboard for mangrove carbon seques
    ```
 2. **Run the dashboard:**
    ```bash
-   python dashboard/app.py
+   PYTHONPATH=. python dashboard/app.py
    ```
    The terminal will display a public share link.
 
+   **Note:** The `PYTHONPATH=.` is required to ensure the `er_model_core` module can be found.
+
 ## Growth Models
 - **Declining Increment (ACTIVE):**
   - Annual increment declines linearly to zero; total size is the sum of non-negative increments (never decreases or goes negative).