docs(architecture): add backend frontend layout

Author: tranhoangpich

README.md

@@ -669,6 +669,7 @@ The design goal is to keep scanning concerns, report rendering, and AI-agent onb
 We initialized a clean layout for a future backend/frontend split while keeping the current Rust crate stable:
 
 - `apps/cli` placeholder for the CLI app crate
+- `apps/backend` placeholder for the Rust HTTP API (uploads + scan)
 - `packages/core` placeholder for the Rust engine + rules crate
 - `apps/frontend` placeholder for a web UI or TUI shell
 - `editors/vscode` for the current VS Code extension

docs/ARCHITECTURE.md

@@ -7,6 +7,7 @@ This repo is evolving into a multi-surface product: a Rust backend (scanner + en
 ```
 apps/
   cli/            # Rust CLI entrypoint (voc)
+  backend/        # Rust HTTP API (uploads + scan)
   frontend/       # Web UI or TUI shell (future)
 packages/
   core/           # Rust engine + rules + report model

docs/STRUCTURE.md

@@ -4,6 +4,7 @@
 .
 ├── apps/
 │   ├── cli/            # CLI app shell (future workspace split)
+│   ├── backend/        # Rust HTTP API for uploads + scan
 │   └── frontend/       # Web UI or TUI shell (future)
 ├── packages/
 │   └── core/           # Rust engine + rules + reports (future)