docs: reorganize documentation into server/ and web/ directories

- docs: move server docs to docs/server/ and update all cross-references
- docs: move web-roadmap.md to docs/web/roadmap.md and create
  docs/web/decisions.md
- docs: update AGENTS.md with separate Server and Web sections

docs/web/roadmap.md

@@ -0,0 +1,49 @@
+# Web Roadmap
+
+## Product Boundary
+
+- The Web client is a pure client-side rendered single-page application.
+- Vite produces static assets only. The project does not use SSR, React Server Components, a Node API server, or a browser-specific business backend.
+- The Web client consumes the same versioned REST API as future Android and other native clients.
+- Production may serve `web/dist` from MyGO or a reverse proxy.
+- Shared API contracts should remain client-neutral and eventually be described by OpenAPI.
+
+## Foundation
+
+The initial project contains only the framework and styling foundation:
+
+- Node.js 24 and npm
+- Vite
+- React
+- TypeScript in strict mode
+- TanStack Query provider
+- Tailwind CSS 4 through its Vite plugin
+- Ant Design provider and components
+- Oxlint from the Vite template
+
+Ant Design owns reusable UI components and theme tokens. Tailwind CSS is initially limited to application layout, spacing, and responsive utilities.
+
+## Planned Structure
+
+```text
+web/src/
+├── app/          # Router, providers, and application composition
+├── api/          # API client and generated contracts
+├── components/   # Shared presentation components
+├── features/     # Auth, files, account, and admin features
+├── pages/        # Route entry points
+├── lib/          # Framework-independent utilities
+└── test/         # Shared test setup and fixtures
+```
+
+## Deferred Dependencies
+
+Some dependencies are suggested for future implementation. Refer these only when the corresponding feature is implemented and propose better choices if any:
+
+- `@ant-design/icons`: Add Ant Design-consistent application and action icons when real screens require them.
+- `openapi-typescript`: Generate TypeScript API types from the shared OpenAPI document.
+- `openapi-fetch`: Provide a small type-safe Fetch client based on generated OpenAPI types.
+- `openapi-react-query`: Connect generated OpenAPI operations to TanStack Query if handwritten query adapters become repetitive.
+- `zustand`: Manage a cross-route upload queue, bulk selection, or other complex client-only state if React state is insufficient.
+- `vitest`: Run unit and integration tests using the Vite toolchain.
+- `pdfjs-dist`: Preview PDF files in the browser when document preview is implemented.