Add contact antispam and fix gallery video playback.

English-only messages, rate limiting, min fill time, and normalized email
validation; improve modal video serving with posters, correct MIME types, and
no gzip on gallery media.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/internal/contact/validate_test.go

@@ -12,16 +12,33 @@ func TestParse_valid(t *testing.T) {
 	}
 }
 
+func TestParse_normalizesEmail(t *testing.T) {
+	sub, errs := Parse("Jimmy", "Jane Doe <jane@example.com>", "Hello there, this is a test message.")
+	if errs.Any() {
+		t.Fatalf("unexpected errors: %v", errs)
+	}
+	if sub.Email != "jane@example.com" {
+		t.Fatalf("email = %q", sub.Email)
+	}
+}
+
 func TestParse_shortMessage(t *testing.T) {
 	_, errs := Parse("Jimmy", "jim@example.com", "short")
-	if !errs.Any() {
-		t.Fatal("expected validation error")
+	if errs["message"] == "" {
+		t.Fatal("expected message error")
 	}
 }
 
 func TestParse_invalidEmail(t *testing.T) {
-	_, errs := Parse("Jimmy", "not-an-email", "This message is long enough to pass.")
+	_, errs := Parse("Jimmy", "not-an-email", "This message is long enough to pass validation here.")
 	if errs["email"] == "" {
 		t.Fatal("expected email error")
 	}
 }
+
+func TestParse_notEnglish(t *testing.T) {
+	_, errs := Parse("Jimmy", "jim@example.com", "これは日本語のテストメッセージです。十分な長さがあります。")
+	if errs["message"] == "" {
+		t.Fatal("expected English-only message error")
+	}
+}