feat: Implement price list management and import functionality

- Added ListinoRelationManager for managing price lists associated with models.
- Introduced ImportaListiniAction for importing price lists from Excel files.
- Created ListinoPrezzo model to represent price entries in the database.
- Developed ListinoExcelParser for parsing Excel files containing price lists.
- Implemented ListinoImporter to handle the import logic and associations.
- Added migration for creating listino_prezzi table and converting measures to mm.
- Updated frontend logic to handle new price list features and validations.
- Enhanced tests for price list import and conversion functionalities.

CLAUDE.md

@@ -60,8 +60,8 @@ Entry point is `src/js/starter.js`, loaded from `src/index.html`. Flow on load (
    `flipView` (180° GSAP-animated turn between front/back view), `addMarker` (in-scene hotspot with a video
    popup).
 6. **`PriceCalculator`** (`src/js/price_calculator.js`) is a stateless-ish module (single module-level
-   `listini` cache set via `init`) that looks up a base price from a width/height grid (`listino.json`,
-   rounded up to the nearest 10cm) and layers on percentage/flat supplements for finish, glass, hinges, handle
+   `listini` cache set via `init`) that looks up a base price from a width/height grid in **mm** (served by
+   the backoffice API, using the first grid size ≥ the requested one) and layers on percentage/flat supplements for finish, glass, hinges, handle
    height, and actuator type, then adds 22% VAT.
 
 ### Data conventions