docs(agile): initialize docs

docs/architecture/high-level-architecture.md

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+# 2. High Level Architecture
+
+## Technical Summary
+
+Project SYSTEM is a monolithic, self-hosted web application built on the Nuxt 4 framework. The architecture is designed for efficiency and transparency, running on a Raspberry Pi. It features a Vue-based frontend interacting with a PostgreSQL database via Nuxt's server-side API routes. The core of the system is an immutable, event-sourced "Main Ledger" where every action is a cryptographically signed transaction, ensuring data integrity and auditability. Identity management is decentralized, based on public/private key pairs.
+
+## Platform and Infrastructure Choice
+
+*   **Platform:** Self-hosted on a user-provided **Raspberry Pi** (Model 4+).
+*   **Key Services:**
+    *   **Application Server:** **Nuxt 4** running in Node.js mode.
+    *   **Database:** **PostgreSQL**.
+    *   **Containerization:** The entire stack will be managed and deployed via **Docker Compose**. This ensures a consistent and reproducible environment.
+*   **Deployment Host and Regions:** Single host, located within the "Община's" private network.
+
+## Repository Structure
+
+*   **Structure:** **Monorepo**.
+*   **Monorepo Tool:** Not required for this level of simplicity. A single `package.json` at the root will manage all dependencies.
+*   **Package Organization:** A standard Nuxt 4 project structure will be used, as detailed in the Frontend Architecture. Server-side logic will reside within the `server/` directory.
+
+## High Level Architecture Diagram
+
+```mermaid
+graph TD
+    subgraph "Browser"
+        A[Citizen's Browser]
+    end
+
+    subgraph "Raspberry Pi (Docker Compose)"
+        B[Nuxt 4 Server]
+        C[PostgreSQL Database]
+
+        B -- "Serves Frontend" --> A
+        A -- "API Calls ($fetch)" --> B
+        B -- "Reads/Writes" --> C
+    end
+
+    style B fill:#2D3748,stroke:#fff,stroke-width:2px,color:#fff
+    style C fill:#4A5568,stroke:#fff,stroke-width:2px,color:#fff
+```
+
+---