Scan floating IPs in the background, page by page, so thousands of addresses work

The "Scan Floating IP" button failed with a client timeout: the project now
holds ~6.4k floating IPs and the scan listed them all in one unpaginated,
timeout-less Neutron request on the HTTP request context.

openstack: ListFreeFloatingIPs reads marker-based pages (fields= keeps them
small) with per-page retry/backoff on transport errors, 5xx and 429, and every
request now has a timeout (also ends hangs inside the orchestrator tick).

orchestrator: the scan is a single-flight background job on the process
context with progress (clearing/listing/enqueuing/done/error), dry_run, full
discovery before anything is enqueued, then SubmitIPs in chunks of 500 in
ascending IP order; a failed read leaves the queue untouched. The auto-cycle
gets a "scanning" phase that polls the job, so the control loop and
autoCycleMu are never held across OpenStack/DB work; it recovers after a
restart and waits for (instead of adopting) a scan started by someone else.

db: migration 0009 (indexes), paged ListIPsPage/ListRegistryPage, GROUP BY
counters, EXISTS completion check, set-based ClearAllIPs.

API: POST /admin/ips/scan -> 202 (dry_run, wait), GET /admin/ips/scan, paging
and filters on /admin/ips and /admin/registry (bare arrays without limit),
results_by_overall in /admin/status.

dashboard: scan progress panel and dry-run button, paginated /ips and
/registry with server-side filters, Overview on counters and capped lists
with progress/ETA, "select all N by filter", hx-params fix for per-row
buttons, real counts in confirmations.

Also: docs (API, USAGE, DASHBOARD, README), plan and review under
docs/changes/, bin/ rebuilt with new SHA256SUMS.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

cmd/control-api/main.go

@@ -59,6 +59,9 @@ func run(configPath string, log *slog.Logger) error {
 	}
 
 	orch := orchestrator.New(database, osClient, cfg, log)
+	// Background jobs (the floating-IP scan) live as long as the process, not
+	// as long as the HTTP request or loop iteration that started them.
+	orch.SetContext(ctx)
 
 	adminToken := os.Getenv(cfg.Auth.AdminTokenEnv)
 	agentToken := os.Getenv(cfg.Auth.AgentTokenEnv)
@@ -135,8 +138,10 @@ func runOrchestratorLoop(ctx context.Context, orch *orchestrator.Orchestrator, c
 			} else if ac.Enabled {
 				continue
 			}
-			if _, _, err := orch.ScanFloatingIPs(ctx); err != nil {
-				log.Error("scan floating ips", "err", err)
+			// Non-blocking: the scan runs in the background (single-flight, so
+			// a still-running scan is simply joined) and must not stall Tick.
+			if st, started := orch.StartScan(orchestrator.ScanOptions{}); !started {
+				log.Info("periodic floating ip scan skipped: a scan is already running", "state", st.State)
 			}
 		}
 	}
@@ -158,11 +163,18 @@ func newOpenStackClient(ctx context.Context, cfg *config.ControlAPI) (openstack.
 }
 
 func newRealOpenStackClient(ctx context.Context, cfg *config.ControlAPI) (openstack.FloatingIPClient, error) {
+	retries := cfg.OpenStack.ListPageRetries
+	if retries < 0 {
+		retries = 0 // negative in the config disables retries
+	}
 	clientCfg := openstack.ClientConfig{
 		AuthURL:   os.Getenv(cfg.OpenStack.AuthURLEnv),
 		ProjectID: os.Getenv(cfg.OpenStack.ProjectIDEnv),
 		Region:    os.Getenv(cfg.OpenStack.RegionEnv),
 		Interface: os.Getenv(cfg.OpenStack.InterfaceEnv),
+
+		RequestTimeout:  time.Duration(cfg.OpenStack.RequestTimeoutSeconds) * time.Second,
+		ListPageRetries: retries,
 	}
 
 	switch cfg.OpenStack.AuthMethod {