DC-101: Disk Space Monitor + Product Vision

Backend:
- src/monitoring/disk-space-monitor.js: monitors Docker disk usage against
  user-configured budget, auto-cleans at thresholds, breaks down by category
- routes/disk-space.js: GET /disk, GET /disk/breakdown, POST /disk/config,
  POST /disk/cleanup endpoints
- src/app.js: wire DiskSpaceMonitor into startup, 10-min check interval
- All 1539 tests pass

Product Vision (PRODUCT-VISION.md):
- DashCaddy is a self-hosting platform, not just a dashboard
- Core value: 'Self-host anything in 30 seconds'
- Three pillars: One-click deploy, zero-config networking, self-healing infra
- vs Portainer/CasaOS/Yunohost positioning

New backlog tasks (P5 tier, DC-101–108):
- Disk budget, one-click deploy with auto Caddyfile+DNS, container
  auto-discovery, app catalog, smart wizard, visual Caddy builder,
  disaster recovery, multi-host fleet management

47 total backlog tasks, ~110 hr of work, cron running every 2h.

dashcaddy-api/routes/disk-space.js

@@ -0,0 +1,64 @@
+const express = require('express');
+const { success, error: errorResponse } = require('../src/utils/responses');
+
+/**
+ * Disk space management routes
+ *
+ * GET  /disk                 — current usage snapshot (budget, breakdown, status)
+ * GET  /disk/breakdown       — detailed breakdown incl. per-container log sizes
+ * GET  /disk/config          — get disk budget settings
+ * POST /disk/config          — update disk budget settings
+ * POST /disk/cleanup         — trigger manual cleanup (standard|aggressive|logs-only)
+ */
+module.exports = function({ diskSpaceMonitor, asyncHandler, log }) {
+  const router = express.Router();
+
+  // Current disk usage snapshot
+  router.get('/', asyncHandler(async (req, res) => {
+    const snapshot = await diskSpaceMonitor.getSnapshot();
+    success(res, snapshot);
+  }, 'disk-get'));
+
+  // Detailed breakdown (includes per-container log sizes)
+  router.get('/breakdown', asyncHandler(async (req, res) => {
+    const breakdown = await diskSpaceMonitor.getDetailedBreakdown();
+    success(res, breakdown);
+  }, 'disk-breakdown'));
+
+  // Get disk budget config
+  router.get('/config', asyncHandler(async (req, res) => {
+    success(res, diskSpaceMonitor.getConfig());
+  }, 'disk-config-get'));
+
+  // Update disk budget config
+  router.post('/config', asyncHandler(async (req, res) => {
+    const { diskBudgetGB, warningThresholdPct, criticalThresholdPct, autoCleanup, enabled, cleanupAggressivePct } = req.body;
+
+    const updates = {};
+    if (typeof diskBudgetGB === 'number' && diskBudgetGB > 0) updates.diskBudgetGB = Math.min(diskBudgetGB, 1000);
+    if (typeof warningThresholdPct === 'number') updates.warningThresholdPct = Math.min(Math.max(warningThresholdPct, 50), 99);
+    if (typeof criticalThresholdPct === 'number') updates.criticalThresholdPct = Math.min(Math.max(criticalThresholdPct, 60), 99);
+    if (typeof cleanupAggressivePct === 'number') updates.cleanupAggressivePct = Math.min(Math.max(cleanupAggressivePct, 70), 99);
+    if (typeof autoCleanup === 'boolean') updates.autoCleanup = autoCleanup;
+    if (typeof enabled === 'boolean') updates.enabled = enabled;
+
+    const config = diskSpaceMonitor.configure(updates);
+    log.info('disk', 'Disk budget updated', updates);
+
+    success(res, { message: 'Disk budget updated', config });
+  }, 'disk-config-set'));
+
+  // Manual cleanup trigger
+  router.post('/cleanup', asyncHandler(async (req, res) => {
+    const level = req.body?.level || 'standard';
+    if (!['standard', 'aggressive', 'logs-only'].includes(level)) {
+      return errorResponse(res, 'Invalid cleanup level. Use: standard, aggressive, or logs-only', 400);
+    }
+
+    log.info('disk', 'Manual cleanup triggered', { level, by: req.auth?.user || 'api' });
+    const result = await diskSpaceMonitor.performCleanup(level);
+    success(res, result);
+  }, 'disk-cleanup'));
+
+  return router;
+};