add architecture documentation and testing strategy

Co-authored-by: Copilot <copilot@github.com>

docs/7-deployment-view.md

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+# 7. Deployment View
+
+Describes:
+
+1. Technical infrastructure used to execute your system, with infrastructure elements like geographical locations, environments, computers, processors, channels and net topologies.
+2. Mapping of (software) building blocks to that infrastructure elements.
+
+## Infrastructure Level 1
+
+```text
+┌─────────────────────────────────────────────┐
+│  Host / VM                                  │
+│  ┌─────────────┐  ┌─────────────────────┐   │
+│  │  frontend   │  │      backend        │   │
+│  │  (Flask)    │  │    (FastAPI)        │   │
+│  │  :5000      │  │    :8000            │   │
+│  └──────┬──────┘  └──────────┬──────────┘   │
+│         │                   │              │
+│         └────────┬──────────┘              │
+│                  │                         │
+│          ┌───────▼────────┐                │
+│          │  db (DuckDB)   │                │
+│          │  data/app.db   │                │
+│          └────────────────┘                │
+└─────────────────────────────────────────────┘
+```
+
+**Motivation:** All three components run on a single VM (or as Docker containers) for simplicity and low operational overhead.
+
+**Quality and/or Performance Features:** The frontend and backend are stateless; DuckDB persists data on the host filesystem.
+
+**Mapping of Building Blocks to Infrastructure:**
+
+| Building Block  | Container / Process          | Port |
+| --------------- | ---------------------------- | ---- |
+| Flask frontend  | `frontend`                   | 5000 |
+| FastAPI backend | `backend`                    | 8000 |
+| DuckDB          | File on host (`data/app.db`) | —    |
+
+## Infrastructure Level 2
+
+### Docker Compose (alternative)
+
+All three services can be run with `docker compose up`. The `backend` mounts the `data/` volume for DuckDB persistence.