Make /templates work like a listing people buy from #419

/templates has a search box and category chips. Measured against the listings people actually buy from, that is about a third of what a listing page needs, and 87 visitors a month are already landing on it.

What Webflow, ThemeForest, Framer and Wix all have and we do not:

• Two filter axes, not one. Type (one page, multi page, launch, store) and industry (portfolio, agency, clinic, cafe, trades). Industry is the axis buyers search by, and both Squarespace and Wix lead with it.
• A count beside every filter value. Webflow's category page is persuasive for no other reason.
• Sort. Newest, and something standing in for popular once we can measure it honestly.
• Filter state in the URL, so a filtered view can be linked and shared.
• A full screen preview with desktop, tablet and phone switching. This is the single most expected feature on a template listing, and we have no device switching anywhere.
• On the template page: the list of pages included, grouped, once Export more than one page #412 lands. Buyers read that list before anything else.

Done when: both axes filter with live counts, the URL carries the filter state, the preview switches device widths against the real exported page rather than a mockup, and nothing scrolls sideways at 390.