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

web/src/lib/api/client.ts

@@ -81,6 +81,23 @@ export interface Settings {
 	created_at: number;
 }
 
+export interface BalanceAdjustment {
+	id: string;
+	delta_ms: number;
+	note: string;
+	effective_at: number; // unix ms
+	created_at: number;
+	updated_at: number;
+}
+
+export interface BalanceSummary {
+	total_delta_ms: number;
+	weeks_delta_ms: number;
+	adjustments_delta_ms: number;
+	closed_week_count: number;
+	adjustment_count: number;
+}
+
 // ─── Entries ─────────────────────────────────────────────────────────────────
 
 export const entries = {
@@ -125,7 +142,18 @@ export const weeks = {
 	},
 	close: (weekKey: string) => request<ClosedWeek>('POST', `/weeks/${weekKey}/close`),
 	reopen: (weekKey: string) => request<void>('DELETE', `/weeks/${weekKey}/close`),
-	balance: () => request<{ total_delta_ms: number; closed_week_count: number }>('GET', '/weeks/balance')
+	balance: () => request<BalanceSummary>('GET', '/weeks/balance')
+};
+
+// ─── Balance adjustments ─────────────────────────────────────────────────────
+
+export const balance = {
+	list: () => request<BalanceAdjustment[]>('GET', '/balance/adjustments'),
+	create: (body: { delta_ms: number; note?: string; effective_at?: number }) =>
+		request<BalanceAdjustment>('POST', '/balance/adjustments', body),
+	update: (id: string, body: { delta_ms: number; note?: string; effective_at?: number }) =>
+		request<BalanceAdjustment>('PUT', `/balance/adjustments/${id}`, body),
+	delete: (id: string) => request<void>('DELETE', `/balance/adjustments/${id}`)
 };
 
 // ─── Settings ────────────────────────────────────────────────────────────────