feat: add background tasks monitoring dashboard

Adds a unified view of all background tasks (imports and test runs)
under Platform Monitoring. Includes real-time status polling,
statistics overview, and task history.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

static/admin/js/background-tasks.js

@@ -0,0 +1,128 @@
+/**
+ * Background Tasks Monitoring Component
+ * Manages the background tasks monitoring page
+ */
+
+// Use centralized logger
+const backgroundTasksLog = window.LogConfig.createLogger('BACKGROUND-TASKS');
+
+function backgroundTasks() {
+    return {
+        // Extend base data
+        ...data(),
+
+        // Set current page for navigation
+        currentPage: 'background-tasks',
+
+        // Page-specific data
+        loading: false,
+        error: null,
+        filterType: null,
+        pollInterval: null,
+
+        // Statistics
+        stats: {
+            total_tasks: 0,
+            running: 0,
+            completed: 0,
+            failed: 0,
+            tasks_today: 0,
+            avg_duration_seconds: null,
+            import_jobs: {},
+            test_runs: {}
+        },
+
+        // Tasks
+        tasks: [],
+        runningTasks: [],
+
+        async init() {
+            backgroundTasksLog.info('Initializing background tasks monitor');
+            await this.loadStats();
+            await this.loadTasks();
+            await this.loadRunningTasks();
+
+            // Poll for updates every 5 seconds
+            this.pollInterval = setInterval(() => {
+                this.loadRunningTasks();
+                if (this.runningTasks.length > 0) {
+                    this.loadStats();
+                }
+            }, 5000);
+        },
+
+        destroy() {
+            if (this.pollInterval) {
+                clearInterval(this.pollInterval);
+            }
+        },
+
+        async loadStats() {
+            try {
+                const stats = await apiClient.get('/admin/background-tasks/tasks/stats');
+                this.stats = stats;
+                backgroundTasksLog.info('Stats loaded:', stats);
+            } catch (err) {
+                backgroundTasksLog.error('Failed to load stats:', err);
+            }
+        },
+
+        async loadTasks() {
+            this.loading = true;
+            this.error = null;
+
+            try {
+                let url = '/admin/background-tasks/tasks?limit=50';
+                if (this.filterType) {
+                    url += `&task_type=${this.filterType}`;
+                }
+
+                const tasks = await apiClient.get(url);
+                this.tasks = tasks;
+                backgroundTasksLog.info('Tasks loaded:', tasks.length);
+            } catch (err) {
+                backgroundTasksLog.error('Failed to load tasks:', err);
+                this.error = err.message;
+
+                if (err.message.includes('Unauthorized')) {
+                    window.location.href = '/admin/login';
+                }
+            } finally {
+                this.loading = false;
+            }
+        },
+
+        async loadRunningTasks() {
+            try {
+                const running = await apiClient.get('/admin/background-tasks/tasks/running');
+                this.runningTasks = running;
+
+                // Update elapsed time for running tasks
+                const now = new Date();
+                this.runningTasks.forEach(task => {
+                    if (task.started_at) {
+                        const started = new Date(task.started_at);
+                        task.duration_seconds = (now - started) / 1000;
+                    }
+                });
+            } catch (err) {
+                backgroundTasksLog.error('Failed to load running tasks:', err);
+            }
+        },
+
+        async refresh() {
+            await this.loadStats();
+            await this.loadTasks();
+            await this.loadRunningTasks();
+        },
+
+        formatDuration(seconds) {
+            if (seconds === null || seconds === undefined) return 'N/A';
+            if (seconds < 1) return `${Math.round(seconds * 1000)}ms`;
+            if (seconds < 60) return `${Math.round(seconds)}s`;
+            const minutes = Math.floor(seconds / 60);
+            const secs = Math.round(seconds % 60);
+            return `${minutes}m ${secs}s`;
+        }
+    };
+}