feat: Add extensible multi-pipeline integration system

This commit implements a plugin-like pipeline architecture with:

Pipeline Core Package (packages/pipeline-core/):
- BasePipeline abstract class all pipelines implement
- PipelineRegistry for database-backed discovery/management
- PipelineRunner for execution with status tracking
- DashboardConfig contracts for dynamic widget definitions

Database Migration (006_pipeline_registry.sql):
- pipeline.registry table for registered pipelines
- pipeline.executions table for execution history
- Views for execution stats and monitoring

ReviewIQ Pipeline Refactor:
- Implements BasePipeline interface
- Adds get_dashboard_config() with widget definitions
- Adds get_widget_data() methods for all dashboard widgets
- Maintains backward compatibility with Pipeline alias

Generic Pipeline API (api/routes/pipelines.py):
- GET /api/pipelines - List all registered pipelines
- GET /api/pipelines/{id} - Pipeline details
- POST /api/pipelines/{id}/execute - Execute pipeline
- GET /api/pipelines/{id}/dashboard - Dashboard config
- GET /api/pipelines/{id}/widgets/{w} - Widget data
- GET /api/pipelines/{id}/executions - Execution history

Frontend Dynamic Dashboard System:
- DynamicDashboard component renders from config
- WidgetRegistry maps types to components
- Widget components: StatCard, LineChart, BarChart,
  PieChart, DataTable, Heatmap
- Pipeline API client library

Frontend Pipeline Pages:
- /pipelines - List all registered pipelines
- /pipelines/[id] - Dynamic dashboard for pipeline
- /pipelines/[id]/executions - Execution history
- Pipelines nav item in Sidebar

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

web/components/dashboard/widgets/PieChart.tsx

@@ -0,0 +1,106 @@
+'use client';
+
+import {
+  PieChart as RechartsPieChart,
+  Pie,
+  Cell,
+  Tooltip,
+  Legend,
+  ResponsiveContainer,
+} from 'recharts';
+import type { WidgetConfig, ChartData, PieChartConfig } from '@/lib/pipeline-types';
+import { WidgetWrapper } from './WidgetWrapper';
+
+interface PieChartWidgetProps {
+  config: WidgetConfig;
+  data: ChartData | null;
+  loading: boolean;
+  error?: string;
+  onRefresh?: () => void;
+}
+
+// Default colors for pie slices
+const DEFAULT_COLORS = [
+  '#3b82f6', // blue
+  '#22c55e', // green
+  '#ef4444', // red
+  '#eab308', // yellow
+  '#8b5cf6', // purple
+  '#ec4899', // pink
+  '#06b6d4', // cyan
+  '#f97316', // orange
+];
+
+/**
+ * Pie/Donut chart widget using Recharts.
+ */
+export function PieChartWidget({
+  config,
+  data,
+  loading,
+  error,
+  onRefresh,
+}: PieChartWidgetProps) {
+  const chartConfig = config.config as PieChartConfig;
+  const chartData = data?.data || [];
+  const colors = chartConfig.colors || DEFAULT_COLORS;
+  const innerRadius = chartConfig.inner_radius || 0; // 0 = pie, > 0 = donut
+
+  // Transform data to use consistent keys
+  const transformedData = chartData.map((item) => ({
+    name: item[chartConfig.label_key] as string,
+    value: item[chartConfig.value_key] as number,
+  }));
+
+  return (
+    <WidgetWrapper config={config} loading={loading} error={error} onRefresh={onRefresh}>
+      {transformedData.length === 0 ? (
+        <div className="flex items-center justify-center h-full text-gray-500">
+          No data available
+        </div>
+      ) : (
+        <ResponsiveContainer width="100%" height="100%">
+          <RechartsPieChart>
+            <Pie
+              data={transformedData}
+              cx="50%"
+              cy="50%"
+              innerRadius={innerRadius}
+              outerRadius="80%"
+              dataKey="value"
+              nameKey="name"
+              label={
+                chartConfig.show_labels !== false
+                  ? ({ name, percent }) => `${name} ${(percent * 100).toFixed(0)}%`
+                  : undefined
+              }
+              labelLine={chartConfig.show_labels !== false}
+            >
+              {transformedData.map((_, index) => (
+                <Cell
+                  key={`cell-${index}`}
+                  fill={colors[index % colors.length]}
+                />
+              ))}
+            </Pie>
+            <Tooltip
+              contentStyle={{
+                backgroundColor: 'white',
+                border: '1px solid #e5e7eb',
+                borderRadius: '0.375rem',
+              }}
+              formatter={(value: number) => [value.toLocaleString(), 'Count']}
+            />
+            {chartConfig.show_legend !== false && (
+              <Legend
+                layout="horizontal"
+                verticalAlign="bottom"
+                align="center"
+              />
+            )}
+          </RechartsPieChart>
+        </ResponsiveContainer>
+      )}
+    </WidgetWrapper>
+  );
+}