Serve /apps/:slug instead of /apps/:id

[v0l]

Closes #94.

No backend change needed — ApiApp.name (lnvps_api/src/api/apps.rs:65) is already documented as the URL/DNS-safe slug; the frontend just never used it as the route param.

• src/routes.tsx — /apps/:id → /apps/:slug.
• src/loaders.ts appLoader — no by-slug endpoint, so it reads the same public catalog appsLoader/homeLoader already fetch and cache (listApps()), and finds the row by name. One less endpoint hit than before, not one more.
• src/pages/app.tsx — the client-side refresh effect needed the numeric id for getApp/deployment filtering; now reads it off the loader's already-resolved app.id instead of re-parsing the URL param. Canonical URL uses the slug.
• src/utils/app-seo.ts appJsonLd, src/pages/account-apps.tsx AppCard, src/pages/blossom-server-hosting.tsx's CTA — all three build the app URL off app.name now instead of app.id/BlossomAppId.
• server/gen-sitemap.ts — easy to miss since it's outside src/: fetches the raw catalog itself for the sitemap, was pulling .id. bun run build's generated sitemap.xml confirmed slug-based, not stale.

Verified server-rendered, not just the build: curl on /apps/strfry and /apps/route96 — real <title>, <h1>, canonical <link> and JSON-LD url, all slug-based. /apps listing's card links and the Blossom CTA both point at the new URLs.

One thing to flag, not decided here: old numeric URLs (/apps/2) now resolve to the same empty/noindex state as any unknown id — no redirect to the slug. If any of these are already indexed or linked externally, that's lost link equity until re-crawled. Didn't add a redirect since the issue didn't ask for one and I don't know if these URLs have any real backlinks yet.

bun test 45 pass (incl. a new appJsonLd test and updated gen-sitemap fixtures), tsc --noEmit clean, build clean at d830c60.