clouds3d-only cleanup: drop Vanta/three.js/clouds2d, real-sky fixes, settlement lights, dynamic location anchor

README.md

@@ -4,6 +4,10 @@ An animated desktop background that runs in a browser. Features:
 
 - Time-of-day simulation with realistic color gradients driven by the
   actual sun position (computed from latitude/longitude via SunCalc).
+- WebGL flight scene (`vendor/clouds3d.js`): raymarched cloud deck, 3D
+  terrain from Copernicus DEM, real star sky (Yale BSC + Milky Way),
+  moon with phases, animated highway car lights and settlement lights
+  from OpenStreetMap/Overpass at night.
 - Night brightness coupled to the moon phase (new moon = minimum, full
   moon = maximum), with a configurable minimum so the night is never
   pitch-black.
@@ -17,7 +21,7 @@ An animated desktop background that runs in a browser. Features:
   to add a new theme.
 - Customisable location: set `CONFIG.location.lat/lon`, or let the
   browser's geolocation API pick one up automatically (falls back to
-  London).
+  the built-in default Passau).
 - Optional custom location label (`CONFIG.location.label`) that
   overrides the OpenStreetMap reverse-geocoding lookup.
 - Configurable digital clock format string using ISO-8601-ish tokens
@@ -60,6 +64,11 @@ window.CONFIG = {
         lon: 13.4319,                  // longitude, -180 to +180, east positive
         label: ''                       // optional custom place name;
                                        // if set, skips reverse-geocoding
+    },
+    orbit: {                           // omit/null = straight-line flight
+        radiusKm: 15,                  // circular flight around location;
+                                       // clamped to ~50 km at zoom 11
+        clockwise: true                // turn direction
     }
 };
 ```
@@ -116,14 +125,13 @@ DDDD   weekday full name    (Monday, Montag, ...)
 ├── ash.css                  default color theme
 ├── gruvbox.css              alternative color theme
 ├── nord.css                 alternative color theme
-├── noise.png                background noise texture for Vanta
-├── vendor/                  vendored third-party JS (no network needed)
-│   ├── three.min.js         MIT (three.js)
+├── vendor/                  vendored third-party files (no network needed)
+│   ├── clouds3d.js          WebGL scene: raymarched clouds, 3D terrain,
+│   │                        real sun/moon/stars, car + city lights
 │   ├── suncalc.js           ISC (SunCalc by mourner)
-│   ├── vanta.clouds.min.js  MIT (Vanta.js Clouds)
-│   ├── vanta.clouds2.min.js MIT (Vanta.js Clouds2)
+│   ├── stars.json           Yale Bright Star Catalogue subset
 │   └── LICENSE              per-library license attributions
-├── default.conf             nginx server config (port 58881)
+├── default.conf             nginx server config (port 58881, tile CORS proxies)
 ├── Dockerfile               builds nginx:alpine image
 └── docker-compose.yml          one-service Compose file
 ```
@@ -131,9 +139,11 @@ DDDD   weekday full name    (Monday, Montag, ...)
 ## Licenses
 
 - **Background application code**: MIT
-- **three.js** (vendored): MIT - <https://github.com/mrdoob/three.js>
 - **SunCalc** (vendored): ISC - <https://github.com/mourner/suncalc>
-- **Vanta.js** (vendored): MIT - <https://github.com/tengbao/vanta>
 - **Open-Meteo** (weather API): CC BY 4.0 - <https://open-meteo.com/>
+- **OpenStreetMap** (basemap tiles, Overpass road/place data): ODbL -
+  <https://www.openstreetmap.org/copyright>
+- **Copernicus DEM** (terrain via terrarium tiles): open data
+- **NASA GIBS VIIRS** (optional night-lights overlay): public domain
 - **OpenStreetMap Nominatim** (reverse geocoding): ODbL -
   <https://nominatim.org/release/>