feat: environmental telemetry charts and resend failed message (#88)

[rinchen]

Summary

Implements two feature-parity items from issue #88 (matching Ian's meshtastic-cli):

• Environmental telemetry — capture, store, and visualize EnvironmentMetrics packets (BME280/BME680/weather stations) with per-node latest readings and time-series charts
• Resend failed message — one-click retry for messages that failed RF/device delivery

Changes

src/renderer/lib/types.ts

• New EnvironmentTelemetryPoint interface with all protobuf env fields: temperature, relativeHumidity, barometricPressure, gasResistance, iaq, lux, windSpeed, windDirection, windGust, windLull, weight, rainfall1h, rainfall24h
• Seven new optional env_* fields on MeshNode (session-only, not persisted to DB — no schema change required)

src/renderer/hooks/useDevice.ts

• Extended onTelemetryPacket type cast to include all env metric fields
• New environmentMetrics variant handler: records time-series into environmentTelemetry state (capped at MAX_TELEMETRY_POINTS), and patches per-node env_* fields on MeshNode via updateNodes
• New environmentTelemetry: EnvironmentTelemetryPoint[] exported from the hook

src/renderer/components/TelemetryPanel.tsx

• New props: environmentTelemetry, useFahrenheit, onToggleFahrenheit
• toF() helper for Celsius → Fahrenheit conversion
• °C/°F toggle button in the panel header — only visible when temperature data is present; state persists to localStorage['mesh-client:useFahrenheit']
• Three new charts (rendered only when the relevant data exists):
  1. Temperature & Humidity — dual Y-axis (°C or °F left, % right)
  2. Barometric Pressure — single Y-axis (hPa)
  3. Air Quality (IAQ) — single Y-axis 0–500
• CSV export extended with env_temperature_c, env_humidity_pct, env_pressure_hpa, env_iaq columns
• Empty-state check and point counter include env data

src/renderer/components/NodeInfoBody.tsx

• iaqLabel() helper maps IAQ score (0–500) to human-readable category (Excellent → Severely Polluted)
• New useFahrenheit?: boolean prop
• Environment section rendered below route info when any env field is set on the node; shows temperature (°C/°F), humidity, pressure, IAQ with label, lux, and wind (speed + direction if available)
• Works in both NodeDetailModal and MapPanel Leaflet popups automatically

src/renderer/components/NodeDetailModal.tsx

• New useFahrenheit?: boolean prop threaded through to NodeInfoBody

src/renderer/components/ChatPanel.tsx

• New onResend: (msg: ChatMessage) => void prop
• Resend button (circular-arrow SVG) appears inline with the status badge when msg.status === 'failed' (device/RF transport failure only — not triggered by MQTT-only failure). Clicking calls onResend(msg) with stopPropagation.

src/renderer/App.tsx

• useFahrenheit state with localStorage persistence
• toggleFahrenheit callback (stable via useCallback)
• handleResend callback — calls device.sendMessage with original payload, channel, and to (DM destination if set)
• All new props wired: TelemetryPanel, NodeDetailModal, ChatPanel

src/renderer/components/ChatPanel.test.tsx

• Added onResend: vi.fn() to the default test props to satisfy the new required prop

Test plan

• Connect to a network with a BME280/BME680/weather-station node; open Telemetry tab — new charts appear once env packets arrive
• Open Node Detail for an env-equipped node — Environment section shows latest temp/humidity/pressure/IAQ/lux/wind
• Toggle °C/°F button in Telemetry header — charts and node detail update; preference survives reload
• Send a message, disconnect mid-send to force failure — circular-arrow icon appears left of the ✗ badge; click it — a new pending message is queued
• npm run build:renderer — no TypeScript or lint errors
• npm test — all 66 tests pass

Fixes #88