@

feat(panel): move a delivery's details onto its own page

The delivery log now lists what identifies a message and nothing else —
time, sender, recipient, subject, status — and links each row to
/deliveries/{id}, which carries the rest: the sending domain, the
application it was submitted under, the Postfix queue id to search the
system log for, and when the status was last reported. Domain and
application were a column each; they were the widest thing in the table
after the addresses and repeat down every filtered page, and they remain
the log's two filters. Back returns to the page and filters the row was
opened from, rebuilt from the log's own parameters only.

Subjects are now decoded for display as well as on the way in. The milter
has decoded them since 8add005, but the rows it wrote before that still
hold the raw =?utf-8?Q?...?= header, and those are the ones an operator is
most likely to still be reading. The decoder moves to internal/mailhdr,
shared by the milter and the panel; it is idempotent, so a row decoded
once passes through unchanged.

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

internal/mailhdr/subject_test.go

@@ -0,0 +1,38 @@
+package mailhdr
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestDecodeSubject(t *testing.T) {
+	long := strings.Repeat("я", SubjectMaxRunes+10)
+
+	for _, tc := range []struct {
+		name, raw, want string
+	}{
+		{"plain", "Hello there", "Hello there"},
+		{"utf8 q", "=?utf-8?Q?=D0=9F=D1=80=D0=BE=D0=B2=D0=B5=D1=80=D0=BA=D0=B0?=", "Проверка"},
+		{"utf8 b, folded across two words", "=?utf-8?B?0J/RgNC40LLQtdGC?=\r\n =?utf-8?B?INC80LjRgA==?=", "Привет мир"},
+		// No decoder for the legacy single-byte charsets: keep the header as
+		// sent rather than losing the subject entirely.
+		{"unknown charset", "=?windows-1251?B?z/Do4uXy?=", "=?windows-1251?B?z/Do4uXy?="},
+		{"too long", long, strings.Repeat("я", SubjectMaxRunes) + "…"},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := DecodeSubject(tc.raw); got != tc.want {
+				t.Fatalf("DecodeSubject(%q) = %q, want %q", tc.raw, got, tc.want)
+			}
+		})
+	}
+}
+
+// The panel decodes on the way out as well as the milter on the way in, so
+// every already-decoded row in the send log passes through a second time.
+func TestDecodeSubjectIsIdempotent(t *testing.T) {
+	for _, s := range []string{"Проверка", "Hello there", "", "=?windows-1251?B?z/Do4uXy?="} {
+		if got := DecodeSubject(DecodeSubject(s)); got != DecodeSubject(s) {
+			t.Fatalf("second pass over %q changed it to %q", s, got)
+		}
+	}
+}