Import payments per member from a GnuCash file

Adds a "Zahlungen importieren" button to the member Zahlungen tab that opens
a dedicated window: point it at a GnuCash file (plain or gzip-compressed
XML, defaults to the file configured in Optionen), pick one of its accounts,
and narrow the account's bookings down with a description-contains filter
and an optional date range.

Each matching booking gets a checkbox to mark it for import as a payment.
Before anything is ticked, bookings are cross-checked against this member's
existing payments by date + amount; a match is highlighted and its checkbox
is refused, so re-importing the same statement can't create a duplicate
payment. Only bookings with a positive amount on the selected account are
offered, since those are the ones that make sense as an incoming payment.

Parsing lives in ccma.services.gnucash_import, independent of the UI, and
is covered by tests against a synthetic GnuCash XML fixture (plain and
gzip-compressed) -- no gnucash/piecash dependency needed since the native
file format is just XML.

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

src/ccma/ui/member_tab.py

@@ -7,6 +7,7 @@ from decimal import Decimal
 from pathlib import Path
 from tkinter import messagebox, ttk
 
+from ccma.config import AppConfig
 from ccma.domain.contributions import (
     CLAIM_STATUS_LABELS,
     DONATION_STATUS_LABELS,
@@ -30,6 +31,7 @@ from ccma.ui.donation_dialog import (
     DonationPaymentDialog,
 )
 from ccma.ui.file_open import open_path
+from ccma.ui.gnucash_import_dialog import GnuCashImportDialog
 from ccma.ui.labels import display_label, storage_key
 from ccma.ui.messages import MessageAction, MessageBannerList, TabMessage
 from ccma.ui.payment_dialog import PaymentCreateDialog, PaymentEditDialog
@@ -62,6 +64,7 @@ class MemberTab(ttk.Frame):
         master: tk.Misc,
         repository: MemberRepository,
         member_id: str,
+        config: AppConfig,
         on_close: Callable[[], None],
         on_changed: Callable[[], None],
         on_open_claim: Callable[[str, str], None],
@@ -72,6 +75,7 @@ class MemberTab(ttk.Frame):
         super().__init__(master, padding=12)
         self.repository = repository
         self.member_id = member_id
+        self.config = config
         self.on_close = on_close
         self.on_changed = on_changed
         self.on_open_claim = on_open_claim
@@ -325,6 +329,10 @@ class MemberTab(ttk.Frame):
         ttk.Button(payment_actions, text="Zahlung löschen", command=self._delete_selected_payment).pack(
             side="left"
         )
+        ttk.Separator(payment_actions, orient="vertical").pack(side="left", fill="y", padx=10)
+        ttk.Button(
+            payment_actions, text="Zahlungen importieren", command=self._import_payments
+        ).pack(side="left")
 
         donations_tab.columnconfigure(0, weight=1)
         donations_tab.rowconfigure(1, weight=1)
@@ -733,6 +741,11 @@ class MemberTab(ttk.Frame):
     def _create_payment(self) -> None:
         PaymentCreateDialog(self, self.repository, self.member_id, self._payment_changed)
 
+    def _import_payments(self) -> None:
+        GnuCashImportDialog(
+            self, self.repository, self.member_id, self.config, self._payment_changed
+        )
+
     def _payment_changed(self) -> None:
         self.refresh()
         self.on_changed()