feat(icons): add Smart Home / Sensors icon category

Add 27 new icons covering common IoT/Zigbee endpoints: smart plug,
relay, energy meter, solar, door/window sensor, smart lock, smoke
detector, siren, motion radar, presence, vibration, water leak,
humidity, air quality, HVAC vent, fan, AC, smart light, blinds,
doorbell, speaker, remote, garage, valve, weather station, plus
voice assistant and webhook in the existing Automation category.

frontend/src/utils/__tests__/nodeIcons.test.ts

@@ -33,6 +33,22 @@ describe('ICON_REGISTRY', () => {
     expect(keys).toContain('database')  // DB services
     expect(keys).toContain('cctv')      // IP Camera / CCTV
   })
+
+  it('contains Smart Home / Sensors icons', () => {
+    const keys = ICON_REGISTRY.map((e) => e.key)
+    expect(keys).toContain('plug')
+    expect(keys).toContain('smoke')
+    expect(keys).toContain('door')
+    expect(keys).toContain('motion')
+    expect(keys).toContain('leak')
+    expect(keys).toContain('lock-smart')
+    expect(keys).toContain('battery-charging')
+  })
+
+  it('exposes the Smart Home / Sensors category', () => {
+    const categories = ICON_REGISTRY.map((e) => e.category)
+    expect(categories).toContain('Smart Home / Sensors')
+  })
 })
 
 describe('ICON_CATEGORIES', () => {