P1-24: live dashboard — fleet summary tiles + host table

Server-rendered HTML view backed by:
  - new store.FleetSummary aggregating host counts + repo bytes +
    snapshot total + open alerts + last-24h job rollup in two queries.
  - GET /api/hosts (JSON list of hosts in the dashboard projection).
  - GET /api/fleet/summary (JSON aggregate, same shape as above).

The HTML page (web/templates/pages/dashboard.html) renders the four
summary tiles + host table directly from store data — no separate
fetch. Per-row state colour comes from .host-row.{degraded,failed,
offline} which paint a 3px left edge so problem hosts are scannable
without reading. HTMX is loaded into the base layout so per-row
"Run now" buttons can hx-post to /hosts/{id}/run-backup, a thin
HTML wrapper that funnels into a new dispatchJob helper shared
with the JSON /api/hosts/{id}/jobs endpoint.

Empty state (zero hosts) collapses to the "no hosts yet" prompt
with the + Add host CTA — matches the v1 mockup.

Template helpers (internal/server/ui/funcs.go) added for byte
formatting (412 GB / 3.7 TB), relative time (3m ago / 2d ago), and
comma grouping (1,847). Pure Go, no template-magic dependency.

Browser-verified end-to-end with seeded fixture data: five hosts
across all four states render with correct dots, accents, last-
backup pills, sizes, snapshot counts, alerts, tags, and the right
action button (Run now / Retry / Run first / View → / offline).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/server/http/server.go

@@ -88,6 +88,10 @@ func (s *Server) routes(r chi.Router) {
 		// host page can call it; for now just the create endpoint.
 		r.Post("/enrollment-tokens", s.handleCreateEnrollmentToken)
 
+		// Fleet read endpoints — back the dashboard.
+		r.Get("/hosts", s.handleListHosts)
+		r.Get("/fleet/summary", s.handleFleetSummary)
+
 		// Run-now: dispatch a job to a host's agent.
 		r.Post("/hosts/{id}/jobs", s.handleRunNow)
 
@@ -127,6 +131,8 @@ func (s *Server) routes(r chi.Router) {
 		r.Get("/login", s.handleUILoginGet)
 		r.Post("/login", s.handleUILoginPost)
 		r.Post("/logout", s.handleUILogoutPost)
+		// HTMX action endpoint for "Run now" buttons on the dashboard.
+		r.Post("/hosts/{id}/run-backup", s.handleUIRunBackup)
 	}
 }