Redesign the setup flow and consolidate the CSS into one primitives layer

Onboarding asks explicitly for one or two parents and shows one card per
parent for balances; the balance form is per parent with inline
validation; the partner can be filled from the FK deduction or added
from it. Settings and Dashboard reuse the same form.

CSS: bare buttons carry no colour any more; buttons, cards, choice
cards, fields, alerts, badges, eyebrow and modal chrome are defined once
in primitives.css. Media queries live only in responsive.css. A style
guard test blocks hex, !important and stray media queries. Bilingual
fixes: calendar selects size by content, header no longer wraps. Vitest
is capped at four workers.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

frontend/src/context/WorkspaceContext.test.tsx

@@ -59,7 +59,6 @@ const unauthenticated = {
 const workspace: Workspace = {
   id: 'ws1',
   name: 'Our workspace',
-  planningMode: 'couple',
   createdAt: '2026-01-01T00:00:00Z',
 }
 
@@ -373,4 +372,21 @@ describe('WorkspaceContext', () => {
       'useWorkspace must be used inside <WorkspaceProvider>',
     )
   })
+
+  it('bumpPlanVersion increments planVersion, giving hooks watching it a reason to refetch', () => {
+    vi.mocked(useAuth).mockReturnValue(unauthenticated)
+
+    const { result } = renderHook(() => useWorkspace(), { wrapper })
+    expect(result.current.planVersion).toBe(0)
+
+    act(() => {
+      result.current.bumpPlanVersion()
+    })
+    expect(result.current.planVersion).toBe(1)
+
+    act(() => {
+      result.current.bumpPlanVersion()
+    })
+    expect(result.current.planVersion).toBe(2)
+  })
 })