feat: F012 match detail view

Full decision analysis page at /demand/results/:matchId:
- MatchDetailHeader: score, badges, CTA (compare/shortlist), back button
- ExecutiveSummaryPanel: 4-row summary (fit, top reason, tradeoff, next step)
- PropertyOverviewPanel: key facts grid; signal-aware for FUTURE_AVAILABILITY
- NeedAlignmentPanel: comparison table with fit indicators (MATCH/PARTIAL/NO_MATCH)
- ScoreBreakdownPanel: hard/soft scores + modifiers + total (sidebar)
- TradeoffPanel: severity-coded list with mitigation hints
- RiskPanel: risks sorted CRITICAL→LOW with category chips
- MissingInformationPanel: priority-grouped with per-item CTAs
- SourceProvenancePanel: source type, label, URL, freshness
- FutureAvailabilityContextPanel: mandatory disclaimer + signal metadata
- NextActionsPanel: engine-ranked actions + standard actions (sidebar)
- Details button on result cards now navigates to match detail

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

src/components/match-detail/ExecutiveSummaryPanel.tsx

@@ -0,0 +1,57 @@
+import { Box, Paper, Typography } from '@mui/material'
+import { CheckCircle2, AlertTriangle, ArrowRight, Target } from 'lucide-react'
+import type { Match } from '../../domain/match'
+
+interface Props {
+  match: Match
+}
+
+export function ExecutiveSummaryPanel({ match }: Props) {
+  const topReason = match.positiveFactors[0]
+  const topTradeoff = match.tradeoffs?.[0]
+  const nextStep = match.nextBestActions?.[0]
+
+  const rows: { icon: React.ReactNode; label: string; text: string }[] = [
+    {
+      icon: <Target size={15} color="#1e3a5f" />,
+      label: 'Gesamteignung',
+      text: match.explainabilitySummary || `${match.matchStrength}-Match mit ${match.matchScore} Punkten`,
+    },
+    ...(topReason ? [{
+      icon: <CheckCircle2 size={15} color="#1a7a4a" />,
+      label: 'Stärkster Grund',
+      text: topReason.explanation,
+    }] : []),
+    ...(topTradeoff ? [{
+      icon: <AlertTriangle size={15} color="#d97706" />,
+      label: 'Hauptabwägung',
+      text: topTradeoff.concern,
+    }] : []),
+    ...(nextStep ? [{
+      icon: <ArrowRight size={15} color="#7c3aed" />,
+      label: 'Empfohlener nächster Schritt',
+      text: nextStep.description ?? nextStep.label,
+    }] : []),
+  ]
+
+  return (
+    <Paper sx={{ p: 2.5, mb: 2, bgcolor: '#f8fafc', border: '1px solid #e2e8f0' }}>
+      <Typography variant="h6" sx={{ fontWeight: 700, mb: 1.5 }}>Executive Summary</Typography>
+      <Box sx={{ display: 'flex', flexDirection: 'column', gap: 1.25 }}>
+        {rows.map((row, i) => (
+          <Box key={i} sx={{ display: 'flex', alignItems: 'flex-start', gap: 1 }}>
+            <Box sx={{ mt: 0.25, flexShrink: 0 }}>{row.icon}</Box>
+            <Box>
+              <Typography variant="caption" sx={{ fontWeight: 600, color: '#64748b', display: 'block' }}>
+                {row.label}
+              </Typography>
+              <Typography variant="body2">
+                {row.text}
+              </Typography>
+            </Box>
+          </Box>
+        ))}
+      </Box>
+    </Paper>
+  )
+}