fix(library): drop out-of-range years instead of failing the album

Tag-supplied years were being passed straight to Postgres' date column
without validation. Files with corrupt or 5+ digit years (seen in the
wild on a couple of dozen albums) tripped SQLSTATE 22008 and the entire
album upsert failed, dropping every track on those albums from the
library.

Validate the year is within 1..9999 before constructing the date. If
it's outside that window, log a warning naming the album and year, and
insert the album with no release_date — a soft field shouldn't take
down the whole row.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

internal/library/scanner_test.go

@@ -16,6 +16,31 @@ import (
 	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
 )
 
+func TestReleaseDateFromYear(t *testing.T) {
+	cases := []struct {
+		in    int
+		ok    bool
+		label string
+	}{
+		{0, false, "missing tag"},
+		{-1, false, "negative"},
+		{1, true, "lower bound"},
+		{1999, true, "ordinary"},
+		{9999, true, "upper bound"},
+		{10000, false, "five digits"},
+		{99999999, false, "tag corruption"},
+	}
+	for _, c := range cases {
+		got, ok := releaseDateFromYear(c.in)
+		if ok != c.ok {
+			t.Errorf("%s: ok = %v, want %v", c.label, ok, c.ok)
+		}
+		if ok && (!got.Valid || got.Time.Year() != c.in) {
+			t.Errorf("%s: date = %+v, want year=%d", c.label, got, c.in)
+		}
+	}
+}
+
 // TestScanner_Integration exercises walk → tag-parse → upsert → incremental
 // skip against a real Postgres. Gated on MINSTREL_TEST_DATABASE_URL.
 func TestScanner_Integration(t *testing.T) {