Refactor: Frontend-Fundament — Format-Utils, Dialog-Ref, Typen (Phase 3a)

- Neuer lib/format.ts: gb/fmtBytes/fmtSize/fmtEta/fmtCtx zentral; aus
  DashboardView/SystemView/ModelsView entdoppelt und importiert.
- CustomDialog: document.getElementById -> useRef (kein DOM-Query, robuster).
- api.ts: GitInfo/ComponentVersion/Versions typisiert, SystemStatus.versions
  ergänzt; App.tsx nutzt SystemStatus statt any.

tsc grün, Build grün, Dashboard verifiziert (keine Konsolenfehler, Formatierer
rendern identisch).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/views/DashboardView.tsx

@@ -2,13 +2,10 @@ import { useEffect, useState } from "react"
 import { Bot, Cpu, ExternalLink, Brain, Layers, Plus, ShieldAlert, X, Power, Shield, Download, RefreshCw, Check, Coins } from "lucide-react"
 import { api, type SystemStatus, type AgentStatus, type ModelInfo, type Memory, type UpdatesResp, type Job } from "@/lib/api"
 import { cn, resolveExternalUrl } from "@/lib/utils"
+import { gb } from "@/lib/format"
 import { CustomDialog } from "@/components/CustomDialog"
 
 
-function gb(b: number) {
-  return (b / 1024 ** 3).toFixed(1)
-}
-
 function RadialGauge({ value, label, detail }: { value: number; label: string; detail?: string }) {
   const radius = 24
   const circ = 2 * Math.PI * radius