fix(web): keep pagination inside the card and make the logo visible - #18

The alert list rendered one pagination button per page. At 27k alerts
that is 2711 buttons in one unwrapped row, spilling across the whole
viewport. Window the pages: first, last, current +/-1, ellipses. Also
reset to page 1 when the filter changes, so a filtered list cannot show
an empty table behind page buttons from the previous total.

The sidebar logo was loaded from a remote URL, blank whenever that host
is unreachable, and the artwork is a black silhouette on a dark sidebar
either way. Bundle it as web/src/assets/logo.png with the webpack asset
rule and TypeScript declarations, and draw it inverted (white) via CSS.

cargo test is unaffected; web jest suite 54/54 and the production
webpack build pass.