Backfill basic spec fields (power_w, release_year, operating_temp, markets)

[ch-bas]

Standing data-backfill lane for four low-coverage but easy-to-source spec fields (all typically on the datasheet). Joins the #163 index.

Coverage of 2,540 cameras:

Field	Coverage	Notes
power.consumption_w	434 (17%)	Useful for PoE-budget planning
release_year	1,048 (41%)	First-sold year
operating_temp_c	1,284 (50%)	e.g. -30 to 60
markets	1,210 (47%)	ISO region tags

Best done in brand/series batches where the datasheet format is shared. Leave a field undefined when the datasheet doesn't state it — never guess (esp. markets, which is region-availability, not where it could be sold).