[FE-33] Build Admin Workspace CRUD Form with react-hook-form and zod validation

[devwums]

Problem

Admins have no form to create or edit workspaces from the UI. Workspace management requires direct database access or API calls.

Proposed Solution

Create frontend/cntr/WorkspaceForm/WorkspaceForm.tsx. Props: initialData?: WorkspaceFormData, onSubmit: (data: WorkspaceFormData) => void, isSubmitting?: boolean. Fields: name (required), description, capacity (integer 1–500), hourlyRateKobo (shown in ₦), address, amenities (multi-select checkboxes). Uses react-hook-form + zod (both already installed). All implementation must live inside frontend/cntr/.

Acceptance Criteria

• File at frontend/cntr/WorkspaceForm/WorkspaceForm.tsx
• Uses react-hook-form and zod for validation
• Price field shown in ₦ to the user but submitted in kobo
• Capacity validates as a positive integer between 1 and 500
• Edit mode pre-populates all fields from initialData
• Submit button shows a loading state when isSubmitting is true
• Test in frontend/cntr/WorkspaceForm/WorkspaceForm.test.tsx