Add additional Machines list filters

[siemenvdn]

Added the basic filters as described in the #506 feature request I made.

Adds four composable filter dimensions to the Machines page on top of the existing text search. All filter state lives in URL search params so filtered views are fully bookmarkable and shareable.

Params:

• q (text search)
• user (user ID or tag-owned)
• tag (e.g. tag:server)
• status (online / offline / expired)
• route (exit-node / subnet)

All optional and composable.

UI:

Screen.Recording.2026-03-21.at.13.15.16.mov

Changes

• machine-filters.tsx — MachineFilters component renders pill-shaped filter dropdowns as a fragment, slotting directly into the existing flex row. Active filters turn indigo-tinted; clicking a selected item deselects it. Tag dropdown is hidden when no machines have tags.
• use-machine-filter-params.ts — custom hook that is the single source of truth for reading/writing all four filter params, including hasActiveFilters and clearFilters (preserves q).
• overview.tsx — filter predicate in useMemo uses lookup tables (STATUS_MATCH, ROUTE_MATCH) instead of nested if-chains. Reads filter params via the shared hook.