Types: Add Zod schemas for API responses and critical props

[andrejvysny]

Context
Issue #38 requests type guards and runtime validation. The project already depends on zod. Many pages rely on server-provided props via Inertia without runtime validation.

Scope

• Define Zod schemas for key API responses and Inertia page props (e.g., transactions/index, analytics, imports)
• Validate data at entry points (page props/hook responses) and narrow types accordingly
• Provide a small helper to log/report schema mismatches in development

Affected files

• resources/js/types (add schemas)
• resources/js/pages/** (apply parsing where data enters components)
• resources/js/lib/zod-helpers.ts (new)

Acceptance criteria

• Zod schemas exist for at least 3 core pages (transactions, analytics, imports)
• Parsing applied once at page boundary; downstream components receive narrowed types
• No runtime exceptions on valid data; mismatches log useful messages in dev
• Link back to P3: Optimize Frontend Architecture and Performance #38

Labels
area:frontend, area:types, type:enhancement