Add dimmable flag where known

L0001 (Philips LEDBulb) and L0002/L0003 (LAMPTAN Gloss V2) are
documented non-dimmable; L0012 is a halogen and inherently dimmable.
Others stay unknown until checked against their packaging.

lamps/L0001/metrics.json

@@ -2,6 +2,7 @@
   "name": "L0001",
   "ean": "8718696822708",
   "type": "led",
+  "dimmable": false,
   "manufacturer": "Philips",
   "model": "LEDBulb 8W E27 3000K (68W equivalent, 770 lm)",
   "notes": "",

lamps/L0002/metrics.json

@@ -2,6 +2,7 @@
   "name": "L0002",
   "ean": "8850646092349",
   "type": "led",
+  "dimmable": false,
   "manufacturer": "LAMPTAN",
   "model": "LED Bulb Gloss V2 9W E27 Daylight 6500K",
   "notes": "",

lamps/L0003/metrics.json

@@ -2,6 +2,7 @@
   "name": "L0003",
   "ean": "8850646092905",
   "type": "led",
+  "dimmable": false,
   "manufacturer": "LAMPTAN",
   "model": "LED Bulb Gloss V2 9W E27 Warm White 2700K",
   "notes": "Gloss V2 series attribution from retailer listings; verify against packaging.",

lamps/L0012/metrics.json

@@ -2,6 +2,7 @@
   "name": "L0012",
   "ean": "4008321211828",
   "type": "halogen",
+  "dimmable": true,
   "rated": {
     "Power_W": 28,
     "lifetime_h": 2000,