Name Trade Republic uploads by statement period

Trade Republic statements all download as document-N.pdf, which says
nothing about what they hold. traderepublic now implements parser.Namer:
it reads the period from the address block at the top of the first page
("DATE 01 May 2025 - 31 Jul 2026") and names the statement
traderepublic_2025_05_01_2026_07_31, lowercase like the NLB names, so the
folder sorts by start date and two downloads of one statement meet under
one name. The transaction table's own DATE heading never matches, since
no date range follows it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/parser/traderepublic_test.go

@@ -162,3 +162,19 @@ func TestParseTradeRepublicIgnoresAmountsInDescription(t *testing.T) {
 		t.Errorf("description = %q, want the inline figure kept", txns[0].Description)
 	}
 }
+
+// A statement is named after the period in its header; the transaction
+// table's DATE heading, with no dates after it, is not mistaken for it.
+func TestTradeRepublicStatementName(t *testing.T) {
+	header := "NIKOLA PETROV                          DATE            01 May 2025 - 31 Jul 2026\n" +
+		"Ulica 21                               IBAN          DE00000000000000000000\n\n" +
+		"DATE                TYPE       DESCRIPTION              MONEY IN      MONEY OUT           BALANCE\n"
+	if got := tradeRepublicStatementName(header); got != "traderepublic_2025_05_01_2026_07_31" {
+		t.Errorf("name = %q, want traderepublic_2025_05_01_2026_07_31", got)
+	}
+	table := "DATE                TYPE       DESCRIPTION              MONEY IN      MONEY OUT           BALANCE\n" +
+		"01 Jul 2026         Interest   Interest payment         €1.17                           €671.58\n"
+	if got := tradeRepublicStatementName(table); got != "" {
+		t.Errorf("name without a period = %q, want none", got)
+	}
+}