Move odometer into the shared footer

Widget + script + styles live in Base.astro now, so every page ticks;
index.astro is back to just rendering the vault homepage.

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

README.md

@@ -37,9 +37,11 @@ Defaults to the kotov vault copy. On cyrion use `deploy/build.sh`
 `docker compose -f deploy/docker-compose.yml up -d` serves `dist/` on
 port 18100 (`garden-next.c0smere.net` while staging).
 
-## Homepage extras
+## Layout extras
 
-`src/pages/index.astro` renders the vault's `index.md` and appends the
-bandwidth odometer, fed by `https://api.c0smere.net/bandwidth/odometer`.
-The widget animates at the lifetime average rate from a fetched baseline —
-it never reflects live throughput, and hides itself if the API is down.
+Every page carries a left sidebar tree of the whole garden (folders
+collapsible, current page highlighted; flows after the footer on narrow
+screens) and the bandwidth odometer in the footer, fed by
+`https://api.c0smere.net/bandwidth/odometer`. The widget animates at the
+lifetime average rate from a fetched baseline — it never reflects live
+throughput, and hides itself if the API is down.