feat: board-first orchestration with Gateway Bridge, live-update, and flow-board

- GatewayBridgeController: MCP-artiger Kommando-Adapter für Agent-zu-Backend
- TaskBridgeService + LiveUpdateService: SSE Live-Sync + Bridge-Kommandos
- FlowBoard.vue: Board-first orchestration dashboard panel
- live-sync.ts store + live.ts service: SSE-basierte Live-Updates
- Nullability-Warnung in HealthController.cs gefixt
- nginx.conf: SSE-Proxy + CORS für Bridge-Endpunkte
- .gitignore: pnpm/corepack local caches ausgeschlossen
- docs: architecture-board-first-orchestration.md hinzugefügt
- README: Backend Bridge API dokumentiert

frontend/src/services/live.ts

@@ -0,0 +1,94 @@
+import { apiFetch } from './api'
+
+export type LiveEventName = 'snapshot' | 'update' | 'heartbeat'
+export type LiveMode = 'live' | 'polling'
+
+export interface LiveCursorDto {
+  sequence: number
+  timestamp: string
+  mode: LiveMode
+}
+
+export interface LiveUpdateEnvelope {
+  type: string
+  timestamp: string
+  payload: unknown
+  sequence: number
+  channel: string
+}
+
+export interface DashboardLiveEventDto {
+  envelope: LiveUpdateEnvelope
+  cursor: LiveCursorDto
+}
+
+export interface OpenDashboardLiveStreamResult {
+  closed: Promise<void>
+}
+
+export async function openDashboardLiveStream(
+  onEvent: (event: LiveEventName, data: unknown) => void,
+  options: { forUser?: string; notificationLimit?: number; afterSequence?: number | null; signal?: AbortSignal } = {},
+): Promise<OpenDashboardLiveStreamResult> {
+  const params = new URLSearchParams({
+    forUser: options.forUser ?? 'bao',
+    notificationLimit: String(options.notificationLimit ?? 50),
+  })
+  if (typeof options.afterSequence === 'number' && Number.isFinite(options.afterSequence) && options.afterSequence > 0) {
+    params.set('afterSequence', String(options.afterSequence))
+  }
+
+  const response = await apiFetch(`/api/dashboard/live?${params}`, {
+    method: 'GET',
+    headers: { Accept: 'text/event-stream', 'Cache-Control': 'no-cache' },
+    signal: options.signal,
+  })
+
+  if (!response.ok || !response.body) {
+    throw new Error(`Live stream unavailable: HTTP ${response.status}`)
+  }
+
+  const reader = response.body.getReader()
+  const decoder = new TextDecoder()
+  let buffer = ''
+
+  const flushBlock = (block: string) => {
+    const lines = block.split('\n')
+    let eventName: LiveEventName = 'update'
+    const dataLines: string[] = []
+
+    for (const rawLine of lines) {
+      const line = rawLine.trimEnd()
+      if (line.startsWith('event:')) eventName = line.slice(6).trim() as LiveEventName
+      if (line.startsWith('data:')) dataLines.push(line.slice(5).trim())
+    }
+
+    if (!dataLines.length) return
+    try {
+      onEvent(eventName, JSON.parse(dataLines.join('\n')))
+    } catch (error) {
+      console.warn('[live] failed to parse event payload', error)
+    }
+  }
+
+  const closed = (async () => {
+    while (true) {
+      const { value, done } = await reader.read()
+      if (done) break
+
+      buffer += decoder.decode(value, { stream: true })
+      const parts = buffer.split('\n\n')
+      buffer = parts.pop() ?? ''
+      for (const part of parts) {
+        if (part.trim()) flushBlock(part)
+      }
+    }
+
+    if (buffer.trim()) {
+      flushBlock(buffer)
+      buffer = ''
+    }
+  })()
+
+  return { closed }
+}