Add balance adjustments (M8)

- New balance_adjustments table with CRUD store, sync logging, and service methods
- SQL migrations restructured: embed fs.FS from internal/store/migrations/, apply in order via user_version
- WeekService.Balance combines closed-weeks delta + adjustments delta; BalanceSummary breakdown
- Four REST routes: GET/POST /api/balance/adjustments, PUT/DELETE /api/balance/adjustments/{id}
- Dexie schema v2 + sync apply cases for balance_adjustments
- API client: BalanceAdjustment type, balance namespace (list/create/update/delete)
- utils: composeDeltaMs / decomposeDeltaMs helpers + 8 new Vitest tests (19 total, all passing)
- History page: balance card breakdown line + full adjustments section with inline add/edit/delete

internal/store/balance_adjustment_store_test.go

@@ -0,0 +1,128 @@
+package store_test
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/wotra/wotra/internal/domain"
+	"github.com/wotra/wotra/internal/store"
+)
+
+func TestBalanceAdjustmentStoreCRUD(t *testing.T) {
+	db, err := store.Open(":memory:")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	s := store.NewBalanceAdjustmentStore(db)
+	ctx := context.Background()
+	now := time.Now().UnixMilli()
+
+	// SumDelta on empty table.
+	total, count, err := s.SumDelta(ctx)
+	if err != nil {
+		t.Fatalf("SumDelta empty: %v", err)
+	}
+	if total != 0 || count != 0 {
+		t.Fatalf("empty: want (0,0), got (%d,%d)", total, count)
+	}
+
+	// List on empty table returns nil slice, no error.
+	list, err := s.List(ctx)
+	if err != nil {
+		t.Fatalf("List empty: %v", err)
+	}
+	if len(list) != 0 {
+		t.Errorf("List empty: want 0, got %d", len(list))
+	}
+
+	// Create two adjustments.
+	a1 := &domain.BalanceAdjustment{
+		ID: "id-1", DeltaMs: 3_600_000, Note: "carry-over",
+		EffectiveAt: now - 86400000, CreatedAt: now, UpdatedAt: now,
+	}
+	a2 := &domain.BalanceAdjustment{
+		ID: "id-2", DeltaMs: -1_800_000, Note: "",
+		EffectiveAt: now, CreatedAt: now, UpdatedAt: now,
+	}
+	if err := s.Create(ctx, a1); err != nil {
+		t.Fatalf("Create a1: %v", err)
+	}
+	if err := s.Create(ctx, a2); err != nil {
+		t.Fatalf("Create a2: %v", err)
+	}
+
+	// GetByID round-trip.
+	got, err := s.GetByID(ctx, "id-1")
+	if err != nil {
+		t.Fatalf("GetByID: %v", err)
+	}
+	if got.DeltaMs != a1.DeltaMs || got.Note != a1.Note {
+		t.Errorf("GetByID: want {%d,%q}, got {%d,%q}", a1.DeltaMs, a1.Note, got.DeltaMs, got.Note)
+	}
+
+	// GetByID missing.
+	_, err = s.GetByID(ctx, "no-such")
+	if err != store.ErrAdjustmentNotFound {
+		t.Errorf("GetByID missing: want ErrAdjustmentNotFound, got %v", err)
+	}
+
+	// SumDelta with two rows.
+	total, count, err = s.SumDelta(ctx)
+	if err != nil {
+		t.Fatalf("SumDelta: %v", err)
+	}
+	if count != 2 {
+		t.Errorf("count: want 2, got %d", count)
+	}
+	want := int64(3_600_000 - 1_800_000)
+	if total != want {
+		t.Errorf("total: want %d, got %d", want, total)
+	}
+
+	// List returns newest effective_at first (a2 has now, a1 has now-1day).
+	list, err = s.List(ctx)
+	if err != nil {
+		t.Fatalf("List: %v", err)
+	}
+	if len(list) != 2 {
+		t.Fatalf("List len: want 2, got %d", len(list))
+	}
+	if list[0].ID != "id-2" {
+		t.Errorf("List[0]: want id-2, got %s", list[0].ID)
+	}
+
+	// Update a1.
+	a1.DeltaMs = 7_200_000
+	a1.Note = "updated"
+	a1.UpdatedAt = now + 1000
+	if err := s.Update(ctx, a1); err != nil {
+		t.Fatalf("Update: %v", err)
+	}
+	got, _ = s.GetByID(ctx, "id-1")
+	if got.DeltaMs != 7_200_000 || got.Note != "updated" {
+		t.Errorf("after Update: want {7200000,updated}, got {%d,%q}", got.DeltaMs, got.Note)
+	}
+
+	// Update missing.
+	missing := &domain.BalanceAdjustment{ID: "no-such", DeltaMs: 1, UpdatedAt: now}
+	if err := s.Update(ctx, missing); err != store.ErrAdjustmentNotFound {
+		t.Errorf("Update missing: want ErrAdjustmentNotFound, got %v", err)
+	}
+
+	// Delete a2.
+	if err := s.Delete(ctx, "id-2"); err != nil {
+		t.Fatalf("Delete: %v", err)
+	}
+	total, count, _ = s.SumDelta(ctx)
+	if count != 1 || total != 7_200_000 {
+		t.Errorf("after Delete: want (7200000,1), got (%d,%d)", total, count)
+	}
+
+	// Delete missing.
+	if err := s.Delete(ctx, "no-such"); err != store.ErrAdjustmentNotFound {
+		t.Errorf("Delete missing: want ErrAdjustmentNotFound, got %v", err)
+	}
+}