fix: NBSP-Betraege und ParserError bei ungueltigem Datum

- parse_german_amount: Fix non-breaking space (U+00A0) handling in second replace call
  was: .replace(" ", "").replace(" ", "") → now: .replace(" ", "").replace("\xa0", "")
- parse_german_date: Catch ValueError from invalid calendar dates (e.g., 31.02.2026)
  and raise ParserError with "Ungültiges Datum" message instead
- Add test for non-breaking space amount parsing
- Add test for invalid date error handling with pytest.raises

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

finance/tests/test_parser_base.py

@@ -1,7 +1,9 @@
 from datetime import date
 from decimal import Decimal
 
-from app.parsers.base import (ParsedStatement, ParsedTransaction,
+import pytest
+
+from app.parsers.base import (ParsedStatement, ParsedTransaction, ParserError,
                               parse_german_amount, parse_german_date)
 from app.parsers.detect import detect_bank
 from app.parsers.validate import balance_difference, dedup_hash
@@ -12,6 +14,7 @@ def test_parse_german_amount():
     assert parse_german_amount("1.234,56-") == Decimal("-1234.56")
     assert parse_german_amount("12,00 S") == Decimal("-12.00")
     assert parse_german_amount("12,00 H") == Decimal("12.00")
+    assert parse_german_amount("1\xa0234,56") == Decimal("1234.56")
 
 
 def test_parse_german_date():
@@ -19,6 +22,11 @@ def test_parse_german_date():
     assert parse_german_date("03.06.", default_year=2026) == date(2026, 6, 3)
 
 
+def test_parse_german_date_invalid():
+    with pytest.raises(ParserError):
+        parse_german_date("31.02.2026")
+
+
 def test_detect_bank():
     assert detect_bank("... Volksbank Musterstadt eG ...") == "vr"
     assert detect_bank("... Raiffeisenbank ...") == "vr"