**Steps to reproduce:**
* Install  `stock` module.
* Go to  Settings and enable: 
     * Storage Locations (Warehouse).
     * Batch, Wave & Cluster Transfers.
* Create a Product and set its on-hand quantity to 60.
* Go to Inventory → Configuration → Operation Types and create a new operation type:
     * Set Type of Operation to Internal Transfer.
     * In the Barcode App tab, enable Group batch lines.
* Go to Inventory → Operations → Internal Transfers and create a new transfer:
     * Select the newly created Operation Type.
     * Add the created Product with quantity 4.4.
     * Mark the transfer as To Do.
* Create another Internal Transfer with the same configuration:
     * Select the same Operation Type.
     * Add the same Product with quantity 48.8.
     * Mark the transfer as To Do.
* Open the Internal Transfers list view.
* Select both created transfers.
* Click Action → Add to Wave Transfer.
     * Choose A new Wave Transfer and confirm.
* In the popup, select both transfers and add them to the wave.
* Open the Barcode application.
* Open the created operation and select the Batch on the right side
to open the wave transfer in the barcode interface.

**Observed behavior:**
- The grouped line quantity is displayed as 53.99999996 instead of
the expected value(53.2).

**Cause:**
- When the Barcode app loads data,` _createState()` is executed,
which calls `groupLines()`.
- Inside this method, quantities are aggregated using standard
JavaScript floating-point addition:

https://github.com/odoo/enterprise/blob/08d0a7f480046bb489ca69e7b3535e99cb20eee5/stock_barcode_picking_batch/static/src/models/barcode_picking_batch_model.js#L204-L205

- Since JavaScript stores numbers as binary floating-point values,
decimals like 4.4 and 48.8 cannot be represented exactly.
Repeated additions accumulate precision errors, producing results
like 53.99999996 instead of 53.2.

**Fix:**
- Aggregate quantities using `formatFloat` with the barcode precision
before converting them back to floats

- `formatFloat` rounds the value according to the configured precision
of the barcode model, ensuring the intermediate result is normalized
after each addition. Converting the formatted value back with
`parseFloat` guarantees the stored number respects the expected
decimal precision and prevents floating-point accumulation errors.

---
opw-5932329

Forward-Port-Of: odoo/enterprise#110241