swarmexec v1.9.0

Features
- Registry: detect a newer semver tag for version-pinned images, not just
  :latest — the tree shows the concrete target version (e.g. ↑ 2.12.0) and
  inspect offers a one-key update to it.
- TUI: a full keybinding help overlay on "?", reachable everywhere (including
  the inspect view and other overlays); footers front-load the escape hatches
  so they never clip; the service-inspect editors are grouped behind an "a"
  actions menu instead of ~18 case-sensitive keys.
- Site: Docker Hub hints across the landing/docs/release pages, full SEO
  (sitemap.xml, hreflang, canonical, Open Graph/Twitter, JSON-LD), and Umami
  click tracking on the download and repository links.

Fixes
- TUI: Ctrl-C inside a container shell now interrupts the foreground process
  (e.g. tail -f) instead of quitting the whole TUI; sh opens with a PTY.
- TUI: the mouse can select and copy container-shell output again (mouse
  capture is released to the terminal emulator while the shell is open).

Internal
- Refactor: a single confirm() helper backs the two-button dialogs.