Settings: one window for how far back every graph reaches, 1 minute to 24 hours

Each machine keeps 300 points per curve whatever the window, so memory doesn't follow it;
a wider window means wider points, each the average of its bucket rather than one instant
out of it. The hub passes the setting to every machine it manages.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

web/src/api.ts

@@ -82,6 +82,7 @@ export interface Series {
 
 // Dashboard layout. `order` lists module ids top-to-bottom; `hidden` are modules switched
 // off; `hiddenItems` are individual rows ("net:wlp1s0", "fs:/boot/efi", "disk:sda", "temp:chip/label").
+export interface HistoryWindow { seconds: number; points: number; stride_sec: number; min_seconds: number; max_seconds: number }
 export interface DashPrefs { order?: string[]; hidden?: string[]; hiddenItems?: string[]; intervalMs?: number; widgets?: { id: string; type: 'stat' | 'gauge' | 'bar' | 'spark' | 'list'; sensor: string; title?: string }[] }
 
 export interface ServiceUnit { name: string; description: string; load: string; active: string; sub: string; enabled: string; failed: boolean }
@@ -179,6 +180,8 @@ export const api = {
   serviceFile: (unit: string) => req<{ content: string }>('GET', `/api/services/${encodeURIComponent(unit)}/file`),
   serviceLogs: (unit: string, n = 200) => req<LogEntry[]>('GET', `/api/services/${encodeURIComponent(unit)}/logs?n=${n}`),
   serviceAction: (unit: string, action: string) => req<void>('POST', `/api/services/${encodeURIComponent(unit)}/${action}`),
+  historyWindow: () => req<HistoryWindow>('GET', '/api/prefs/history', undefined, true),
+  setHistoryWindow: (seconds: number) => req<HistoryWindow>('PUT', '/api/prefs/history', { seconds }, true),
   dashPrefs: () => req<DashPrefs>('GET', '/api/prefs/dashboard'),
   saveDashPrefs: (p: DashPrefs) => req<void>('PUT', '/api/prefs/dashboard', p),
   login: (password: string) => req<void>('POST', '/api/login', { password }, true),