fix(maps): let users and admins enter a CARTO API key (#2060)

CARTO stamps an "API KEY REQUIRED" watermark onto every basemap tile
fetched without a key since 26.08.2026, and both CartoDB presets plus the
built-in fallback are CARTO. The key is free and needs no account, so add
it as a setting rather than dropping the provider.

carto_api_key sits next to mapbox_access_token: per user in Settings/Map,
instance-wide under Admin/User Defaults, encrypted at rest, injected from
CARTO_API_KEY on managed instances. Unlike Mapbox it never switches the
map provider, since a raster key says nothing about the renderer.

The key is appended as ?key= at render time instead of being stored in the
template, so a saved URL stays portable and survives a rotation. That is
also what reaches the four maps that pinned CARTO and ignored the user's
tile setting: atlas, collections, the public trip share and the public
journey. The two share pages read it from their token-gated payload, the
same way baseCurrency already travels.

Also lifts the release notice above page chrome. Its overlay sat at
z-index 50, under the Vacay mode toolbar at 61, so the dialog was neither
on top nor modal. Adds a six-step layer scale to index.css and moves the
three notice shells onto it.

Closes #2054
Closes #2052

server/scripts/migrate-encryption.ts

@@ -404,7 +404,7 @@ async function main() {
     }
 
     // --- settings: per-user encrypted keys ---
-    const encryptedSettingKeys = ['webhook_url', 'ntfy_token', 'mapbox_access_token', 'llm_api_key'];
+    const encryptedSettingKeys = ['webhook_url', 'ntfy_token', 'mapbox_access_token', 'carto_api_key', 'llm_api_key'];
     const settingRows = db.prepare(
       `SELECT user_id, key, value FROM settings WHERE key IN (${encryptedSettingKeys.map(() => '?').join(', ')})`
     ).all(...encryptedSettingKeys) as { user_id: number; key: string; value: string }[];