feat: Parser-Basis, Bank-Erkennung, Saldo-/Duplikat-Pruefung

- ParsedTransaction und ParsedStatement Datenklassen
- parse_german_amount(): German format number parsing (1.234,56 -> Decimal)
- parse_german_date(): DD.MM.YYYY date parsing with optional year
- detect_bank(): Recognize VR/HVB/DKB from text markers
- balance_difference(): Validate statement balance consistency
- dedup_hash(): SHA256-based transaction deduplication

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

finance/tests/test_parser_base.py

@@ -0,0 +1,48 @@
+from datetime import date
+from decimal import Decimal
+
+from app.parsers.base import (ParsedStatement, ParsedTransaction,
+                              parse_german_amount, parse_german_date)
+from app.parsers.detect import detect_bank
+from app.parsers.validate import balance_difference, dedup_hash
+
+
+def test_parse_german_amount():
+    assert parse_german_amount("1.234,56") == Decimal("1234.56")
+    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")
+
+
+def test_parse_german_date():
+    assert parse_german_date("03.06.2026") == date(2026, 6, 3)
+    assert parse_german_date("03.06.", default_year=2026) == date(2026, 6, 3)
+
+
+def test_detect_bank():
+    assert detect_bank("... Volksbank Musterstadt eG ...") == "vr"
+    assert detect_bank("... Raiffeisenbank ...") == "vr"
+    assert detect_bank("... HypoVereinsbank ...") == "hvb"
+    assert detect_bank("... UniCredit Bank ...") == "hvb"
+    assert detect_bank("... Deutsche Kreditbank AG ...") == "dkb"
+    assert detect_bank("... DKB ...") == "dkb"
+    assert detect_bank("irgendwas") is None
+
+
+def _stmt(txs, opening, closing):
+    return ParsedStatement(bank="vr", iban=None, period_start=None,
+                           period_end=None, opening_balance=opening,
+                           closing_balance=closing, transactions=txs)
+
+
+def test_balance_difference():
+    txs = [ParsedTransaction(date(2026, 6, 1), None, Decimal("-50"), "Miete", "V"),
+           ParsedTransaction(date(2026, 6, 2), None, Decimal("20"), "Gutschrift", "K")]
+    assert balance_difference(_stmt(txs, Decimal("100"), Decimal("70"))) == Decimal("0")
+    assert balance_difference(_stmt(txs, Decimal("100"), Decimal("75"))) == Decimal("5")
+
+
+def test_dedup_hash_normalizes_whitespace():
+    a = dedup_hash(1, date(2026, 6, 1), Decimal("-50.00"), "Miete  Juni")
+    b = dedup_hash(1, date(2026, 6, 1), Decimal("-50.00"), "Miete Juni")
+    assert a == b and len(a) == 64