feat(postgres)!: promote to v1.0.0 — BeginTx with pgx options, Stats, bump all deps to v1.0.0

Add BeginTx(ctx, pgx.TxOptions) to Client interface for explicit isolation level and
read-only transaction control; Begin refactored as a convenience wrapper calling
BeginTx(ctx, pgx.TxOptions{}). Add Stats() *pgxpool.Stat to Component interface for
connection pool observability. Bump all micro-lib dependencies (logz, health, launcher,
xerrors) from v0.9.0 to v1.0.0. API committed as stable.

postgres_test.go

@@ -105,9 +105,10 @@ func (m *mockTx) Rollback(ctx context.Context) error
 
 type mockClient struct{ tx *mockTx }
 
-func (m *mockClient) Begin(ctx context.Context) (Tx, error)         { return m.tx, nil }
-func (m *mockClient) Ping(ctx context.Context) error                { return nil }
-func (m *mockClient) HandleError(err error) error                   { return HandleError(err) }
+func (m *mockClient) Begin(ctx context.Context) (Tx, error)                       { return m.tx, nil }
+func (m *mockClient) BeginTx(ctx context.Context, opts pgx.TxOptions) (Tx, error) { return m.tx, nil }
+func (m *mockClient) Ping(ctx context.Context) error                              { return nil }
+func (m *mockClient) HandleError(err error) error                                 { return HandleError(err) }
 func (m *mockClient) GetExecutor(ctx context.Context) Executor {
 	if tx, ok := ctx.Value(ctxTxKey{}).(Executor); ok {
 		return tx
@@ -149,6 +150,24 @@ func TestUnitOfWork_InjectsExecutor(t *testing.T) {
 	}
 }
 
+// --- BeginTx / Stats ---
+
+func TestComponent_BeginTx_NilPool(t *testing.T) {
+	c := &pgComponent{logger: newLogger()}
+	_, err := c.BeginTx(context.Background(), pgx.TxOptions{})
+	if err == nil {
+		t.Error("expected error for nil pool")
+	}
+}
+
+func TestComponent_Stats_NilPool(t *testing.T) {
+	c := &pgComponent{logger: newLogger()}
+	stats := c.Stats()
+	if stats == nil {
+		t.Error("Stats() should return non-nil zero value when pool is nil")
+	}
+}
+
 // --- helpers ---
 
 func assertCode(t *testing.T, err error, want xerrors.Code) {