feat: LeadVault - zentrale Lead-Datenbank mit CRM-Funktionen

- Prisma-Schema: Lead + LeadEvent Modelle (Migration 20260320)
- lib/services/leadVault.ts: sinkLeadsToVault mit Deduplizierung
- Auto-Sync: alle 4 Pipelines schreiben Leads in LeadVault
- GET /api/leads: Filter, Sortierung, Pagination (Server-side)
- PATCH/DELETE /api/leads/[id]: Status, Priorität, Tags, Notizen
- POST /api/leads/bulk: Bulk-Aktionen für mehrere Leads
- GET /api/leads/stats: Statistiken + 7-Tage-Sparkline
- POST /api/leads/quick-serp: SERP-Capture ohne Enrichment
- GET /api/leads/export: CSV-Export mit allen Feldern
- app/leadvault/page.tsx: vollständige UI mit Stats, Quick SERP,
  Filter-Leiste, sortierbare Tabelle, Bulk-Aktionen, Side Panel
- Sidebar: LeadVault-Eintrag mit Live-Badge (neue Leads)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

prisma/migrations/20260320162355_add_lead_vault/migration.sql

@@ -0,0 +1,56 @@
+-- CreateTable
+CREATE TABLE "Lead" (
+    "id" TEXT NOT NULL PRIMARY KEY,
+    "domain" TEXT,
+    "companyName" TEXT,
+    "contactName" TEXT,
+    "contactTitle" TEXT,
+    "email" TEXT,
+    "linkedinUrl" TEXT,
+    "phone" TEXT,
+    "sourceTab" TEXT NOT NULL,
+    "sourceTerm" TEXT,
+    "sourceJobId" TEXT,
+    "serpTitle" TEXT,
+    "serpSnippet" TEXT,
+    "serpRank" INTEGER,
+    "serpUrl" TEXT,
+    "emailConfidence" REAL,
+    "status" TEXT NOT NULL DEFAULT 'new',
+    "priority" TEXT NOT NULL DEFAULT 'normal',
+    "notes" TEXT,
+    "tags" TEXT,
+    "country" TEXT,
+    "headcount" TEXT,
+    "industry" TEXT,
+    "capturedAt" DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "contactedAt" DATETIME,
+    "updatedAt" DATETIME NOT NULL
+);
+
+-- CreateTable
+CREATE TABLE "LeadEvent" (
+    "id" TEXT NOT NULL PRIMARY KEY,
+    "leadId" TEXT NOT NULL,
+    "event" TEXT NOT NULL,
+    "at" DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    CONSTRAINT "LeadEvent_leadId_fkey" FOREIGN KEY ("leadId") REFERENCES "Lead" ("id") ON DELETE CASCADE ON UPDATE CASCADE
+);
+
+-- CreateIndex
+CREATE INDEX "Lead_domain_idx" ON "Lead"("domain");
+
+-- CreateIndex
+CREATE INDEX "Lead_status_idx" ON "Lead"("status");
+
+-- CreateIndex
+CREATE INDEX "Lead_sourceTab_idx" ON "Lead"("sourceTab");
+
+-- CreateIndex
+CREATE INDEX "Lead_capturedAt_idx" ON "Lead"("capturedAt");
+
+-- CreateIndex
+CREATE INDEX "Lead_email_idx" ON "Lead"("email");
+
+-- CreateIndex
+CREATE INDEX "LeadEvent_leadId_idx" ON "LeadEvent"("leadId");