Open the trail catalog on what is near and well rated, not the longest trails

Part of #1002.

Problem

/trails defaults to longest-first. The first screen of the catalog is therefore:

1. North Country National Scenic Trail (MI) — 1,161.5 mi, HARD
2. North Country National Scenic Trail (OH) — 1,069.7 mi, HARD
3. Grand Enchantment Trail — 1,036.5 mi, HARD
4. Iditarod National Historic Trail — 996.2 mi, HARD

Nobody browsing trails wants a 1,161-mile thru-hike. AllTrails opens on local favourites near you, which is the same catalog making the opposite first impression — and it is the specific comparison that reads as "they look higher quality than us".

The home page already has a Local favorites section, so the catalog page currently disagrees with our own front door.

Acceptance

• Default ordering is near-me first, then well-rated, rather than longest.
• Falls back sensibly with no location: a rated/popular ordering, not distance.
• An explicit sort choice still wins, and the chip reflects what the list is actually sorted by.
• Trails with no rating do not sink below the fold permanently — with 0% rated today (#1002) a pure rating sort is a coin toss, so the tiebreak needs thought.
• The empty and "nothing near you" states say what to do next.

Partly done by ede87f9 ("lay the catalog out like AllTrails' explore page"), which added a Sort chip (Best match, Top rated, Longest, Shortest, Name) and made near-me sort by rating:

sort: sortChoice() || urlSort() || (search() ? 'featured' : near ? 'rating' : 'longest'),

So of the acceptance list:

• Default ordering is near-me first, then well-rated — done for a visitor with a location
• Falls back sensibly with no location — still longest, with the rationale that "nationally there is no such thing as near, so length is what makes the list impressive". That is exactly the first screen this issue was filed about, and it is still what production serves today: 1161.46 mi hard elev=0 North Country National Scenic Trail (MI) 1069.72 mi hard elev=0 North Country National Scenic Trail (OH) 1036.49 mi hard elev=0 Grand Enchantment Trail
• An explicit sort choice still wins, and the chip reflects it
• Trails with no rating do not sink permanently — untouched, and still a coin toss: a fresh 400-trail production sample is 0% rated, so sort: 'rating' currently orders by nothing at all
• Empty / "nothing near you" states — a location-only empty answer now falls back to a global browse

Remaining work is the location-less default and the tiebreak, and the tiebreak is the interesting half: until #1002 lands there is no rating signal to sort on, so it needs a proxy the catalog actually has — length sanity, surface, national-trail status, whether there is a real photo.

Worth noting the gap cuts deeper now: ede87f9, ee9bd40 and 11711421 rebuilt the catalog, trail page and feed around photos, ratings, reviews and elevation, and production has none of the four.