test(db): report why PostgreSQL refused to start before tearing it down

The fixture removes the container as soon as startup fails, so every CI
failure reduced to one line: the container is unhealthy. The server's own
account of the refusal is deleted with it, which leaves a reproducible
staging-gate failure undiagnosable from the log alone.

Print the container log before the teardown runs.

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

frontend/tests/helpers/postgres-fixture.ts

@@ -115,6 +115,16 @@ export function startPostgresFixture(): PostgresFixture {
     );
   } catch (error) {
     try {
+      try {
+        // The teardown below deletes the only account of why the server refused to start.
+        execFileSync(
+          "docker",
+          [...composeArguments, "logs", "--no-color", "--tail", "80", "postgres"],
+          { env: environment, stdio: "inherit" },
+        );
+      } catch {
+        // Preserve the original startup failure.
+      }
       try {
         execFileSync(
           "docker",