feat: Add pipeline execution UI, stage metrics, and API proxy routes

- Add run pipeline page with job selection UI
- Add execution detail page with stage metrics visualization
- Add stage_metrics and total_duration_ms to pipeline.executions table
- Create Next.js API proxy routes for all pipeline endpoints
- Fix trailing slash issues in pipeline-api.ts URLs
- Add Docker volume mounts for pipeline packages
- Add REVIEWIQ_DATABASE_URL and LLM API keys to docker-compose
- Fix JSONB field parsing in execution detail endpoint

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

web/app/api/pipelines/[pipelineId]/execute/route.ts

@@ -0,0 +1,39 @@
+import { NextRequest, NextResponse } from 'next/server';
+
+const API_BASE_URL = process.env.NEXT_PUBLIC_API_URL || 'http://localhost:8000';
+
+export async function POST(
+  request: NextRequest,
+  { params }: { params: Promise<{ pipelineId: string }> }
+) {
+  try {
+    const { pipelineId } = await params;
+    const body = await request.json();
+
+    const url = `${API_BASE_URL}/api/pipelines/${pipelineId}/execute`;
+    const response = await fetch(url, {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+      },
+      body: JSON.stringify(body),
+    });
+
+    if (!response.ok) {
+      const error = await response.json().catch(() => ({ detail: 'Unknown error' }));
+      return NextResponse.json(
+        { error: error.detail || 'Failed to execute pipeline' },
+        { status: response.status }
+      );
+    }
+
+    const data = await response.json();
+    return NextResponse.json(data);
+  } catch (error) {
+    console.error('Pipeline execute API error:', error);
+    return NextResponse.json(
+      { error: 'Failed to execute pipeline' },
+      { status: 500 }
+    );
+  }
+}