Rework: use native res.partner.bank qr_code_method instead of report xpath

Register 'spayd' as a proper qr_code_method on res.partner.bank (same
extension point account_qr_code_sepa uses for EPC/'sct_qr'), sequence=6
so it's tried before EPC (sequence 20). Eligibility now requires CZK/EUR
currency AND a Czech customer country - previously the report template
replaced EPC for *any* customer as long as the invoice currency was CZK
or EUR, which would incorrectly show a Czech SPAYD code to e.g. a German
customer being invoiced in EUR.

account.move._generate_qr_code() already tries all registered methods in
priority order and the existing div#qrcode block in
account.report_invoice_document already renders whatever comes back, so
this needs no report template override at all.

- Move get_cz_qr_code_base64()/cz_to_iban() from account_move.py into
  res_partner_bank.py (as _get_qr_code_generation_params/_spayd_to_iban);
  fix bank_code not being zero-padded to 4 digits, which could throw off
  the mod-97 checksum for short local bank codes. Verified the checksum
  against the standard 19-2000145399/0800 -> CZ6508000000192000145399
  reference example and general IBAN mod-97 validity.
- Remove views/report_invoice.xml (nothing left to override) and the now
  unnecessary qrcode Python dependency (Odoo's own barcode report action
  renders the image; this module only supplies the SPAYD string).
- Update README FAQ to match the new eligibility rule.

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

__manifest__.py

@@ -20,8 +20,12 @@ Key Features:
 -------------
 * **Standard SPAYD Support:** Fully compatible with all major Czech banking apps (ČSOB, Komerční banka, Česká spořitelna, etc.)
 * **Smart IBAN Conversion:** Automatically converts local account numbers (e.g. 123-456/0800) to IBAN format.
-* **Multi-country IBAN Support:** Works with Czech (CZ), Slovak (SK), and other SEPA IBANs.
-* **Integration:** Works with standard Odoo invoice templates.
+* **Multi-country IBAN Support:** Works with Czech (CZ), Slovak (SK), and other IBANs.
+* **Integration:** Registers as a native Odoo QR-code method (res.partner.bank
+  qr_code_method='spayd', same mechanism account_qr_code_sepa uses for EPC) -
+  no changes to the invoice print template are needed, and it's automatically
+  preferred over EPC for Czech customers, falling back to EPC otherwise.
+  Users can still switch manually via the "Payment QR-code" field.
 * **Currency Support:** CZK and EUR (for cross-border payments).
 
 Usage for Slovak Companies:
@@ -37,12 +41,7 @@ Note: Czech banks will process EUR payments if the recipient has a EUR account.
     'author': 'Ash technology s.r.o.',
     'website': 'https://github.com/ash-technology/l10n_cz_extra',
     'license': 'LGPL-3',
-    'external_dependencies': {
-        'python': ['qrcode'],
-    },
-    'data': [
-        'views/report_invoice.xml',
-    ],
+    'data': [],
     'installable': True,
     'auto_install': False,
     'application': False,