feat: Phase 8 - Frontend main views (T-026 to T-031)

Implement all main frontend views for the MITRE ATT&CK coverage platform:

- T-026: Dashboard with coverage summary cards and tactic breakdown table

- T-027: Interactive ATT&CK matrix with filtering by status, tactic, platform

- T-028: Technique detail page with tests, intel items, and review actions

- T-029: Test creation form with technique selector and validation

- T-030: Test detail page with drag and drop evidence upload and download

- T-031: System admin panel with MITRE sync and intel scan controls

New components: CoverageSummaryCard, TacticCoverageChart, AttackMatrix, TechniqueCell, TestForm, EvidenceUpload, EvidenceList

New API modules: metrics.ts, techniques.ts, tests.ts, evidence.ts, system.ts

All views use TanStack Query for data fetching with proper loading and error states. Role-based UI controls for admin/lead actions.

frontend/src/components/EvidenceList.tsx

@@ -0,0 +1,97 @@
+import { FileIcon, Download, ExternalLink, Copy, Check } from "lucide-react";
+import { useState } from "react";
+
+interface Evidence {
+  id: string;
+  test_id: string;
+  file_name: string;
+  sha256_hash: string;
+  uploaded_by: string | null;
+  uploaded_at: string;
+  download_url?: string;
+}
+
+interface EvidenceListProps {
+  evidences: Evidence[];
+  onDownload: (evidenceId: string) => void;
+}
+
+export default function EvidenceList({ evidences, onDownload }: EvidenceListProps) {
+  const [copiedHash, setCopiedHash] = useState<string | null>(null);
+
+  const formatDate = (dateStr: string) => {
+    return new Date(dateStr).toLocaleDateString("en-US", {
+      year: "numeric",
+      month: "short",
+      day: "numeric",
+      hour: "2-digit",
+      minute: "2-digit",
+    });
+  };
+
+  const copyHash = async (hash: string) => {
+    await navigator.clipboard.writeText(hash);
+    setCopiedHash(hash);
+    setTimeout(() => setCopiedHash(null), 2000);
+  };
+
+  if (evidences.length === 0) {
+    return (
+      <div className="rounded-lg border border-gray-800 bg-gray-800/30 p-6 text-center">
+        <FileIcon className="mx-auto h-10 w-10 text-gray-600" />
+        <p className="mt-2 text-sm text-gray-400">No evidence files uploaded yet</p>
+      </div>
+    );
+  }
+
+  return (
+    <div className="space-y-3">
+      {evidences.map((evidence) => (
+        <div
+          key={evidence.id}
+          className="rounded-lg border border-gray-800 bg-gray-800/30 p-4 transition-colors hover:bg-gray-800/50"
+        >
+          <div className="flex items-start justify-between">
+            <div className="flex items-start gap-3">
+              <div className="rounded-lg bg-gray-700 p-2">
+                <FileIcon className="h-5 w-5 text-gray-400" />
+              </div>
+              <div>
+                <p className="font-medium text-gray-200">{evidence.file_name}</p>
+                <p className="mt-0.5 text-xs text-gray-500">
+                  Uploaded {formatDate(evidence.uploaded_at)}
+                </p>
+              </div>
+            </div>
+            <button
+              onClick={() => onDownload(evidence.id)}
+              className="flex items-center gap-1.5 rounded-lg border border-gray-700 bg-gray-800 px-3 py-1.5 text-sm text-gray-300 hover:border-cyan-500/50 hover:text-cyan-400 transition-colors"
+            >
+              <Download className="h-4 w-4" />
+              Download
+            </button>
+          </div>
+
+          {/* SHA256 Hash */}
+          <div className="mt-3 flex items-center gap-2">
+            <span className="text-xs font-medium text-gray-500">SHA256:</span>
+            <code className="flex-1 truncate rounded bg-gray-900 px-2 py-1 font-mono text-xs text-gray-400">
+              {evidence.sha256_hash}
+            </code>
+            <button
+              onClick={() => copyHash(evidence.sha256_hash)}
+              className="rounded p-1 text-gray-500 hover:bg-gray-700 hover:text-gray-300"
+              title="Copy hash"
+            >
+              {copiedHash === evidence.sha256_hash ? (
+                <Check className="h-4 w-4 text-green-400" />
+              ) : (
+                <Copy className="h-4 w-4" />
+              )}
+            </button>
+          </div>
+        </div>
+      ))}
+    </div>
+  );
+}