professionalize repo for public release

- rename ctcloud -> bucketeer everywhere (cmd/bucketeer, binary, compose service)
- group brand assets under assets/ (light/dark logo + UI screenshot)
- move long-form docs under docs/ (ARCHITECTURE, DESIGN, GOAL) and add
  docs/SKILL.md: how an agent queries/audits a running instance and answers
  user questions from the API and PostgreSQL
- README: large logo (light/dark picture) and UI screenshot, repository layout
- .gitignore: /bucketeer, .env, pgdata, build/test artifacts, OS junk
- .dockerignore: keep brand/docs/markdown out of the build context

Dockerfile

@@ -13,10 +13,10 @@ COPY . .
 # Static binary: no cgo, no shell, no writable filesystem required.
 RUN CGO_ENABLED=0 GOOS=linux go build \
         -trimpath -ldflags="-s -w" \
-        -o /out/ctcloud ./cmd/ctcloud
+        -o /out/bucketeer ./cmd/bucketeer
 
 FROM gcr.io/distroless/static-debian12:nonroot
-COPY --from=build /out/ctcloud /ctcloud
+COPY --from=build /out/bucketeer /bucketeer
 USER nonroot:nonroot
 EXPOSE 9090
-ENTRYPOINT ["/ctcloud"]
+ENTRYPOINT ["/bucketeer"]