[ADD] pos_payment_method_cashdro_rounding: migration to 18.0

Migrated from the 17.0 branch (4fbf328). APIs that no longer exist in 18.0:

* `order.selected_paymentline` -> `order.get_selected_paymentline()`
* `ErrorPopup` + `env.services.popup` -> `AlertDialog` + `env.services.dialog`
* `/** @odoo-module */`, implicit in `.esm.js` since 17.0

The rounding itself needed a different approach: `get_rounding_applied()` now
reads `taxTotals.order_rounding`, only computed over payments that are already
`is_done()`. The CashDro line is still `waiting` when the amount is requested,
so a literal port would always have added 0. `getDefaultAmountDueToPayIn()` is
the 18.0 equivalent: it applies `getRoundedRemaining()` honouring both
`cash_rounding` and `only_round_cash_method`, and is what core itself uses for
the default amount of a payment line.

Only `_cashdro_payment_url()` is patched now, instead of duplicating the whole
`cashdro_send_payment_request()`, so the request flow, the acknowledge, the
polling and the error handling stay in the base module. With no cash rounding
configured the patch delegates to `super` and changes nothing.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

pos_payment_method_cashdro_rounding/__manifest__.py

@@ -0,0 +1,18 @@
+{
+    "name": "POS CashDro Rounding",
+    "version": "18.0.1.0.0",
+    "summary": "Apply cash/currency rounding to CashDro payment request amount.",
+    "category": "Point of Sale",
+    "license": "AGPL-3",
+    "author": "Criptomart",
+    "depends": [
+        "point_of_sale",
+        "pos_payment_method_cashdro",
+    ],
+    "assets": {
+        "point_of_sale._assets_pos": [
+            "pos_payment_method_cashdro_rounding/static/src/js/cashdro_rounding.esm.js",
+        ],
+    },
+    "installable": True,
+}