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/ui/funcs.go

@@ -0,0 +1,134 @@
+package ui
+
+import (
+	"fmt"
+	"html/template"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// funcMap returns the template functions every page can call.
+// Kept small on purpose: anything fancier belongs in the handler,
+// which can pre-compute and pass primitives into the view.
+func funcMap() template.FuncMap {
+	return template.FuncMap{
+		"bytes":   formatBytes,
+		"relTime": formatRelTime,
+		"comma":   formatComma,
+		"deref":   derefStr,
+		"timeNotZero": func(t *time.Time) bool { return t != nil && !t.IsZero() },
+	}
+}
+
+// formatBytes renders a byte count as a short human string —
+// "412 GB", "3.7 TB", "8.4 GB". Single decimal place for sub-1000
+// values, none above. Returns "—" for zero so the dashboard's
+// "never run" rows read clean.
+func formatBytes(n int64) template.HTML {
+	if n == 0 {
+		return template.HTML(`<span class="text-ink-fade">—</span>`)
+	}
+	const (
+		kb = 1000
+		mb = 1000 * kb
+		gb = 1000 * mb
+		tb = 1000 * gb
+	)
+	var (
+		val  float64
+		unit string
+	)
+	switch {
+	case n >= tb:
+		val, unit = float64(n)/float64(tb), "TB"
+	case n >= gb:
+		val, unit = float64(n)/float64(gb), "GB"
+	case n >= mb:
+		val, unit = float64(n)/float64(mb), "MB"
+	case n >= kb:
+		val, unit = float64(n)/float64(kb), "kB"
+	default:
+		return template.HTML(fmt.Sprintf(`%d <span class="text-ink-mute text-[11px]">B</span>`, n))
+	}
+	num := strconv.FormatFloat(val, 'f', -1, 64)
+	if val < 100 && !strings.Contains(num, ".") {
+		num += ".0"
+	} else if val < 100 && strings.Contains(num, ".") {
+		// One decimal max, e.g. "3.7" not "3.74".
+		idx := strings.Index(num, ".")
+		if len(num) > idx+2 {
+			num = num[:idx+2]
+		}
+	} else {
+		// Above 100, no decimals — "412" not "412.4".
+		if idx := strings.Index(num, "."); idx > 0 {
+			num = num[:idx]
+		}
+	}
+	return template.HTML(fmt.Sprintf(`%s <span class="text-ink-mute text-[11px]">%s</span>`, num, unit))
+}
+
+// formatRelTime renders a *time.Time as a short relative string like
+// "3m ago" / "2d ago" / "5w ago". Future times render as "in Xs".
+// Nil pointer returns "—".
+func formatRelTime(t *time.Time) string {
+	if t == nil || t.IsZero() {
+		return "—"
+	}
+	d := time.Since(*t)
+	suffix := "ago"
+	if d < 0 {
+		d = -d
+		suffix = "from now"
+	}
+	switch {
+	case d < time.Minute:
+		return fmt.Sprintf("%ds %s", int(d.Seconds()), suffix)
+	case d < time.Hour:
+		return fmt.Sprintf("%dm %s", int(d.Minutes()), suffix)
+	case d < 24*time.Hour:
+		return fmt.Sprintf("%dh %s", int(d.Hours()), suffix)
+	case d < 7*24*time.Hour:
+		return fmt.Sprintf("%dd %s", int(d.Hours()/24), suffix)
+	default:
+		return fmt.Sprintf("%dw %s", int(d.Hours()/(24*7)), suffix)
+	}
+}
+
+// formatComma renders 1847 as "1,847". Used for snapshot counts and
+// any other count that benefits from grouping at this scale.
+func formatComma(n int) string {
+	s := strconv.Itoa(n)
+	if n < 1000 && n > -1000 {
+		return s
+	}
+	// Hand-rolled grouping; Go has no builtin and we don't want a
+	// dep for this. Negative numbers handled by stripping the sign,
+	// grouping, then putting it back.
+	neg := false
+	if s[0] == '-' {
+		neg = true
+		s = s[1:]
+	}
+	var b strings.Builder
+	for i, c := range s {
+		if i > 0 && (len(s)-i)%3 == 0 {
+			b.WriteByte(',')
+		}
+		b.WriteRune(c)
+	}
+	if neg {
+		return "-" + b.String()
+	}
+	return b.String()
+}
+
+// derefStr returns the string a pointer points to, or "" if nil.
+// Avoids "<nil>" appearing in templates that hit a missing FK.
+func derefStr(p *string) string {
+	if p == nil {
+		return ""
+	}
+	return *p
+}