Split compose dev/prod and relax contact form friction.

Use compose.dev.yaml and compose.prod.yaml with fixed Go cache mounts, block sudo make dev, build Air outside app/tmp for rootless Docker, soften English spam checks, and simplify contact error copy.

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

app/internal/contactcheck/form_test.go

@@ -18,8 +18,8 @@ func TestFormFilledTooFast(t *testing.T) {
 	now := time.Unix(1_000_000, 0)
 	seen := now.Add(-MinFormFillDuration).Unix()
 
-	if !FormFilledTooFast(0, now) {
-		t.Error("missing seen time should be too fast")
+	if FormFilledTooFast(0, now) {
+		t.Error("missing seen time should be allowed")
 	}
 	if !FormFilledTooFast(seen+1, now) {
 		t.Error("submit before min duration should be too fast")