feat(nmsr): cut avatar refresh lag to ~1min + document HTTP routes

NMSR has no per-request avatar refresh (the `?skin=` override is ignored by this
build), so the only lever for a changed skin to appear is the resolve cache.
Drop resolve_cache_duration 15m -> 60s so account-page skin changes propagate
within ~1 min; texture cache stays 48h (Drasl skin URLs are content-hashed, so a
new skin is always a new URL — never stale). Cost is one extra internal Drasl
profile lookup per avatar per minute, trivial for 4-10 players.

Update the now-stale "~15 min" copy (skinLead + skinPreviewNote, en/es/eu) and
code comments to "~1 min".

Add plan/19-routes.md: a reference for the nmsr / landing / auth HTTP routes
(public via caddy + browser->Drasl + internal service-to-service), indexed in
plan/00-overview.md.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

plan/00-overview.md

@@ -146,6 +146,7 @@ and uptime-kuma.
 - `15-letsencrypt.md` — Let's Encrypt (OVH DNS-01) + host nginx ingress
 - `17-mod-shortlist.md` — kitchen-sink gap doc + landing mod-list dataset (PLANNED)
 - `18-landing-rework.md` — join flow / rosters / account / mod list / footer (PLANNED)
+- `19-routes.md` — HTTP route reference (nmsr / landing / auth + internal)
 
 ## Boot/dependency order