Switch lamps to internal IDs; EAN becomes optional metadata

Directories rename from bare EANs to L0001..L0010 (measurement order).
metrics.json gains an ean field, and a rated block with advertised
values (flux, CCT, power, lifetime) where already documented, so the
site can show advertised-vs-measured deltas. One EAN can now cover
several lamp versions (variant field) and unbranded lamps need no
barcode.

lamps/L0001/metrics.json

@@ -1,8 +1,16 @@
 {
-  "name": "8718696822708",
+  "name": "L0001",
+  "ean": "8718696822708",
   "manufacturer": "Philips",
   "model": "LEDBulb 8W E27 3000K (68W equivalent, 770 lm)",
   "notes": "",
+  "rated": {
+    "Phi_lm": 770,
+    "CCT_K": 3000,
+    "Power_W": 8,
+    "lifetime_h": 15000,
+    "W_equiv": 68
+  },
   "instrument": "HPCS6500",
   "measured_at": "2026-07-08T12:01:34+07:00",
   "instrument_date": "2026-07-08",