hub v0.64.0 — offsite pool-box aggregate: fill, oversubscription, per-customer bars, operator alert (R-5)

The operator sees the shared pool box's real state on the hub: total box fill vs
capacity, Σ(shared soft quotas) vs capacity (the oversubscription ratio), per-customer
usage/quota bars, and a box-level operator alert (fill % + oversub ratio) on the existing
dispatcher's operator channel. Per-customer fill alerts already existed; the box-level
aggregate was the gap. READ-ONLY against Hetzner (GET only).

Phase-0 probe (gate PASSED): the live pool box 611714 returns capacity via
storage_box_type.size (1 TiB / bx11) and usage via a stats object (size/size_data/
size_snapshots), all bytes; our token reads it (200).

- hetznerapi: additive StorageBoxType + StorageBoxStats on StorageBox (no existing field/
  method changed); fake carries them + a GetBoxCalls counter; golden decode test.
- monitor.OffsiteBoxChecker: OffsiteChecker-sibling for the box; fetch-throttled (1 GET/
  15min), cached BoxSnapshot, escalation-only + recovery re-arm. FILL (used/capacity 80/90)
  + OVERSUB (Σ shared+enabled quotas / capacity, 2.0x) — independent. Σ from the ConfigJSON
  Descriptor (offsite.ReadDescriptor, new), never the report echo; dedicated+disabled
  excluded. Scope "pool-box" -> operator channel only, no SaveEvent. Failed fetch keeps the
  last snapshot degraded; missing data never becomes 0% and never transitions a band.
- config: Alerting.OffsiteBoxFill{Warn,Crit}Percent + OffsiteOversubWarnRatio (80/90/2.0
  defaults; thresholds pending Viktor's ruling). Constructed in the HETZNER_TOKEN branch,
  60s sweep, snapshot handed to the web server.
- web: Offsite-tab panel (fill bar, Σ+ratio, per-customer usage/quota rows) + a compact
  dashboard tile; reads the cached snapshot only, never fetches; nil -> "not configured".

Tests: 10 new + 4 red-proofs (throttle, Σ filter, escalation-only, failed-fetch honesty),
all confirmed red then restored. go build/vet/test all pass; hub confirm gate OK.

hub/internal/web/server.go

@@ -19,6 +19,7 @@ import (
 	"gitea.dooplex.hu/admin/felhom-hub/internal/claim"
 	"gitea.dooplex.hu/admin/felhom-hub/internal/gitea"
 	"gitea.dooplex.hu/admin/felhom-hub/internal/intent"
+	"gitea.dooplex.hu/admin/felhom-hub/internal/monitor"
 	"gitea.dooplex.hu/admin/felhom-hub/internal/poke"
 	"gitea.dooplex.hu/admin/felhom-hub/internal/offsite"
 	"gitea.dooplex.hu/admin/felhom-hub/internal/semver"
@@ -66,6 +67,7 @@ type Server struct {
 	assetsMgr       *assets.Manager
 	gitea           *gitea.Client       // optional; enables the Day-0 artifact version dropdowns
 	offsite         *offsite.Provisioner // optional; enables Hetzner offsite provisioning (SLICE 1)
+	offsiteBox      func() (monitor.BoxSnapshot, bool) // optional (v0.64.0, R-5); the pool-box aggregate snapshot accessor
 	tenantsync      tenancyProvisioner   // optional; enables PBS DR tier provisioning (web/pbsdr.go)
 	claimEngine     *claim.Engine        // optional; enables the customer-claim resend button (v0.50.0)
 	// intentHub (v0.58.0, Direction-2 immediate-sync) is Bumped by every operator-intent handler
@@ -181,6 +183,11 @@ func (s *Server) SetAssetManager(am *assets.Manager) {
 // offsite enabled returns an error (offsite not configured on this hub).
 func (s *Server) SetOffsiteProvisioner(p *offsite.Provisioner) { s.offsite = p }
 
+// SetOffsiteBox wires the pool-box aggregate snapshot accessor (v0.64.0, R-5): the checker's cached
+// snapshot, read on the Offsite tab + the Dashboard tile. nil (no HETZNER_TOKEN/box id) → both render an
+// honest "not configured". The web layer NEVER fetches from Hetzner — it only reads this cache.
+func (s *Server) SetOffsiteBox(fn func() (monitor.BoxSnapshot, bool)) { s.offsiteBox = fn }
+
 // SetClaimEngine wires the customer-claim code engine for the Setup-tab resend button (v0.50.0).
 func (s *Server) SetClaimEngine(e *claim.Engine) { s.claimEngine = e }
 
@@ -742,8 +749,13 @@ func (s *Server) handleDashboard(w http.ResponseWriter, r *http.Request) {
 		data = append(data, dc)
 	}
 
+	payload := struct {
+		Customers   []dashboardCustomer
+		OffsiteTile *offsiteTile // R-5: nil → no tile rendered
+	}{Customers: data, OffsiteTile: s.offsiteBoxTile()}
+
 	w.Header().Set("Content-Type", "text/html; charset=utf-8")
-	if err := s.templates.ExecuteTemplate(w, "dashboard.html", data); err != nil {
+	if err := s.templates.ExecuteTemplate(w, "dashboard.html", payload); err != nil {
 		s.logger.Printf("[ERROR] Template render: %v", err)
 	}
 }