fix: restore history chart initialization after flood bands change

src/static/dashboard.html

@@ -370,30 +370,36 @@
                         level: { type: 'linear', position: 'right', grid: { drawOnChartArea: false } },
                         x: { ticks: { maxTicksLimit: 12 } }
                     },
+                    plugins: {
+                        legend: { display: true },
+                        floodBands: { enabled: true }
+                    }
+                },
                 plugins: [{
-                        id: 'flood-bands',
+                    id: 'floodBands',
-                        beforeDraw(chart) {
+                    beforeDraw(chart, _args, pluginOptions) {
+                        if (!pluginOptions.enabled || !chart.chartArea) return;
                         const levelScale = chart.scales?.level;
-                            if (!levelScale || levelScale.min == null) return;
+                        if (!levelScale || !Number.isFinite(levelScale.min) || !Number.isFinite(levelScale.max)) return;
+                        const { ctx, chartArea } = chart;
                         const zones = [
                             { min: levelScale.min, max: 3.0, color: 'rgba(30,139,96,.08)' },
                             { min: 3.0, max: 4.5, color: 'rgba(217,144,24,.12)' },
                             { min: 4.5, max: levelScale.max, color: 'rgba(204,75,55,.15)' },
                         ];
-                            zones.forEach((z) => {
-                                const top = levelScale.getPixelForValue(Math.min(z.max, levelScale.max));
-                                const bottom = levelScale.getPixelForValue(Math.max(z.min, levelScale.min));
-                                if (bottom > top) {
-                                    const { ctx, chartArea } = chart;
                         ctx.save();
+                        zones.forEach((z) => {
+                            const min = Math.max(z.min, levelScale.min);
+                            const max = Math.min(z.max, levelScale.max);
+                            if (max <= min) return;
+                            const top = levelScale.getPixelForValue(max);
+                            const bottom = levelScale.getPixelForValue(min);
                             ctx.fillStyle = z.color;
                             ctx.fillRect(chartArea.left, top, chartArea.right - chartArea.left, bottom - top);
+                        });
                         ctx.restore();
                     }
-                            });
-                        }
                 }]
-                }
             });
             $('history-status').textContent = rows.length ? `${rows.length} measurements (${sampled.length} daily) from PostgreSQL` : 'No PostgreSQL measurements in this period';
             $('history-card').scrollIntoView({ behavior: 'smooth', block: 'nearest' });