feat(layout): icon rail sidebar + consistent card borders

[WhiteMuush]

Summary

• Unify all top-level card borders to border-border/60 (dashboard widgets style) across alerts, employees, register, reports, settings, credentials and skeletons.
• Replace the sliding overlay sidebar with a permanent 64px icon rail. Each icon reveals its name on hover via a label that slides out from under the panel, with a small ease-in-back "bop" on mouse-leave before tucking back behind the rail.

Details

• Rail layering: shadow z-0 (below labels), labels z-10, opaque surface z-20, icons/pills z-30. The label's left edge stays hidden under the opaque surface; the rail shadow no longer tints the label.
• Removed the now-unused open/close machinery: SidebarContext, the Topbar toggle button, and the auto-close timers.
• Content offset by the rail width (pl-16).

Test plan

• npm run lint passes.
• Manual: hover each icon shows the label sliding out; leaving triggers the bop then hide; alert badge shows on the bell icon; active route highlighted; sign out works.