feat: initialize ingest-api with Koa and telemetry handling

- Create ingest-api with Koa framework for handling device telemetry.
- Implement telemetry ingestion with MongoDB, Redis, and PostgreSQL.
- Add API endpoints for telemetry and health checks.
- Set up testing with Vitest for unit and end-to-end tests.
- Configure Prettier and ESLint for code formatting and linting.
- Create Docker Compose setup for PostgreSQL, MongoDB, and Redis services.
- Establish contracts package for shared Zod schemas and TypeScript types.
- Implement React frontend with device status and greeting functionalities.
- Add VS Code setup documentation for onboarding developers.

docs/architecture.md

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+# Architecture
+
+Copy this layout for later device + dashboard projects.
+
+## Lanes
+
+- **Device lane:** `apps/ingest-api` (Koa) — firmware / gateways POST JSON.
+- **User lane:** `apps/crud-api` (Express) — React, humans, billing later.
+- **Shared types:** `packages/contracts` (Zod only). No Koa, Express, Mongo, or trest.
+
+Frontend people can run `yarn workspaces focus web` and do not need the private trest registry.
+
+## Data flow
+
+```mermaid
+flowchart LR
+  subgraph devices [Device lane]
+    D[Device / demo ping]
+    I[Koa ingest-api :3001]
+    D -->|POST /telemetry JSON| I
+  end
+
+  subgraph stores [Stores]
+    M[(MongoDB raw telemetry)]
+    R[(Redis hot key TTL)]
+    P[(PostgreSQL device_current_state)]
+    A[(PostgreSQL analytics — not in this repo)]
+  end
+
+  subgraph humans [User lane]
+    W[React web :5173]
+    C[Express crud-api :3000]
+    W -->|axios GET /greeting GET /devices/:id/status| C
+  end
+
+  I -->|insert event| M
+  I -->|SET device:id EX 15s| R
+  I -->|UPSERT current row| P
+  M -.->|ETL cron later| A
+  C -->|SELECT snapshot| P
+  C -->|GET device:id| R
+```
+
+Near-real-time product path (Postgres + Express is enough at this scale):
+
+```mermaid
+sequenceDiagram
+  participant D as Device
+  participant I as ingest-api Koa
+  participant PG as Postgres
+  participant C as crud-api Express
+  participant W as React
+  D->>I: POST /telemetry
+  I->>PG: UPSERT device_current_state
+  W->>C: GET /devices/dev-1/status poll 1s
+  C->>PG: SELECT by device_id
+  C->>W: lastSeen payload source postgres
+```
+
+Redis is compared on the Devices page. It is not required for the UI to look live.
+
+## Demo dual-write (do not copy blindly)
+
+Ingest writes Mongo first, then Redis and Postgres best-effort. A 200 can still mean Redis or Postgres missed. Production should derive those from a queue. This handler is a teaching shortcut.
+
+Redis TTL expiry means “no recent ping.” Redis restart looks like everyone is offline. Postgres still has `device_current_state`.
+
+Ingest may only upsert that snapshot table. CRUD owns greeting / future users and orgs.
+
+Hourly Mongo → Postgres analytics is the dotted ETL box. Not implemented.
+
+## Ports
+
+| Service    | Port  |
+| ---------- | ----- |
+| crud-api   | 3000  |
+| ingest-api | 3001  |
+| web        | 5173  |
+| postgres   | 5432  |
+| mongo      | 27017 |
+| redis      | 6379  |
+
+## Run
+
+```bash
+docker compose up -d
+yarn install
+yarn dev:crud
+yarn dev:ingest
+yarn dev:web
+```
+
+Open `http://127.0.0.1:5173/devices`, click **Ping dev-1**, watch Postgres and Redis columns. Wait 15s without pinging: Redis goes offline, Postgres keeps the last row.