Add CLAUDE.md project onboarding guide

Build commands, architecture overview, library gotchas, and conventions
for the firmware, backend, and frontend components.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -0,0 +1,95 @@
+# Tau Acuvim - IoT Power Meter Monitoring System
+
+## What This Is
+
+IoT platform for monitoring Acuvim II power meters via ESP32 devices. Three components:
+
+1. **Firmware** (`firmware/`) - ESP32-WROVER-B (TTGO T-Call v1.4) C++ firmware, PlatformIO + Arduino
+2. **Console Backend** (`console/src/Tau.Acuvim.Console/`) - .NET 10 minimal API + PostgreSQL
+3. **Console Frontend** (`console/frontend/`) - React 18 + TypeScript + Vite + Ant Design 5
+
+## Build & Run
+
+### Firmware
+```bash
+cd firmware
+pio run                    # Build
+pio test -e native         # Run unit tests (28 tests)
+pio run -t upload          # Flash to ESP32
+pio run -t uploadfs        # Upload SPIFFS (captive portal)
+```
+
+### Console Backend
+```bash
+cd console/src/Tau.Acuvim.Console
+dotnet build
+dotnet run                 # Starts on http://localhost:5000
+```
+
+### Console Tests
+```bash
+cd console/tests/Tau.Acuvim.Console.Tests
+dotnet test                # 23 xUnit tests
+```
+
+### Console Frontend
+```bash
+cd console/frontend
+npm install
+npm run dev                # Dev server on http://localhost:5173, proxies to :5000
+npm run build              # Production build to dist/
+```
+
+### Docker (Production)
+```bash
+cd console
+docker compose -f docker-compose.prod.yml up -d
+```
+
+## Architecture
+
+### Firmware
+- RS485 Modbus RTU reads Acuvim II registers (IEEE 754 Float32)
+- WiFi STA+AP concurrent mode; GSM/GPRS failover via TinyGSM/SIM800L
+- MQTT for telemetry (QoS 0), commands (QoS 1), heartbeat, alerts
+- SD card offline buffering (JSONL, non-blocking drain)
+- OTA updates with dual partition rollback; watchdog + crash loop detection
+- Captive portal provisioning at 192.168.4.1
+
+### Console Backend
+- Minimal API pattern — endpoints in `Endpoints/*.cs`, services in `Services/*.cs`
+- PostgreSQL via EF Core with Npgsql; JSONB columns for telemetry data
+- MQTTnet 5.x bridge (`MqttBridgeService`) subscribes to device topics
+- SignalR hub at `/hubs/devices` for real-time frontend updates
+- JWT auth with rate limiting on auth endpoints
+
+### Console Frontend
+- Pages in `src/pages/`, components in `src/components/`
+- API layer in `src/api/`, hooks in `src/hooks/`
+- TanStack Query for data fetching with SignalR cache invalidation
+- ECharts for telemetry visualization
+
+## Key Conventions
+
+- **No development without explicit user instruction** — do not proactively add features or refactor
+- Firmware pin assignments are in `firmware/include/pin_config.h` — authoritative source
+- Modbus register map is in `firmware/include/acuvim_registers.h`
+- MQTT topic structure: `acuvim/{device_id}/{topic}` — protocol spec in `docs/mqtt-protocol.md`
+- 20 MQTT commands defined in `firmware/src/command_handler.cpp`
+- Swagger UI available at `/swagger` in development
+
+## Library Gotchas
+
+- **Swashbuckle 10.x**: Uses `Microsoft.OpenApi` namespace (not `Microsoft.OpenApi.Models`). `AddSecurityRequirement` takes a factory delegate. See Program.cs.
+- **MQTTnet 5.x**: `PayloadSegment` has no getter — use `Payload.ToArray()` with `System.Buffers`.
+- **EF Core InMemory + JsonDocument**: Needs `ValueConverter<JsonDocument?, string?>` — see `TestHelpers.cs`.
+
+## Specs & Docs
+
+- 10-phase specification: `docs/acuvim-spec-01.md` through `docs/acuvim-spec-10.md`
+- Deployment: `docs/deployment-guide.md`
+- Field installation: `docs/device-commissioning.md`
+- MQTT protocol: `docs/mqtt-protocol.md`
+- Wiring: `docs/hardware-wiring.md`
+- Troubleshooting: `docs/troubleshooting.md`
+- Integration tests: `docs/integration-test-scenarios.md`