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/lib/pipeline-api.ts

@@ -166,6 +166,26 @@ export async function listExecutions(
   return response.json();
 }
 
+/**
+ * Get a specific execution by ID.
+ */
+export async function getExecution(
+  pipelineId: string,
+  executionId: string
+): Promise<ExecutionStatus> {
+  const url = `${API_BASE}/api/pipelines/${pipelineId}/executions/${executionId}`;
+  const response = await fetch(url);
+
+  if (!response.ok) {
+    if (response.status === 404) {
+      throw new Error(`Execution not found: ${executionId}`);
+    }
+    throw new Error(`Failed to fetch execution: ${response.statusText}`);
+  }
+
+  return response.json();
+}
+
 /**
  * Enable a pipeline.
  */