Deploy main eacf1e7 to prod

Replaces #559, which conflicted.

Model: opus-5-5

internal/database/password_test.go

@@ -192,6 +192,39 @@ func TestHashPasswordUniqueness(t *testing.T) {
 	}
 }
 
+// TestHashPassword_ShippedParameters hashes and verifies through
+// HashPassword at the shipped Argon2id parameters. Every other test
+// hashes at the lower memory cost a test binary uses, so this is the
+// one that keeps production hashing covered. One hash and one
+// verification: each costs 64 MB.
+//
+//nolint:paralleltest // changes the hashing cost for the whole binary
+func TestHashPassword_ShippedParameters(t *testing.T) {
+	database.HashAtShippedCostForTest(t)
+
+	password := "correct horse battery staple"
+
+	hash, err := database.HashPassword(password)
+	if err != nil {
+		t.Fatalf("hashing with the shipped parameters: %v", err)
+	}
+
+	const shipped = "$argon2id$v=19$m=65536,t=1,p=4$"
+
+	if !strings.HasPrefix(hash, shipped) {
+		t.Errorf("hash = %q, want prefix %q", hash, shipped)
+	}
+
+	valid, err := database.VerifyPassword(password, hash)
+	if err != nil {
+		t.Fatalf("VerifyPassword() error = %v", err)
+	}
+
+	if !valid {
+		t.Error("VerifyPassword() returned false for correct password")
+	}
+}
+
 // TestVerifyDummyPassword_DoesRealWork covers the anti-enumeration
 // path. Login charges an unknown username a verification against a
 // dummy hash so that a nonexistent account is not answered in