Rework analytics chart scaling; self-contained SVG charts

- Charts render as single SVGs with axis labels inside the viewBox,
  replacing the stretched plot + HTML overlay labels
- Rolling ranges end at now, t0 aligned to UTC day; bucket size follows
  the window (6h up to 31 days) so "all" at its 30-day minimum renders
  identically to "month"
- X labels always centered on their true position; no edge-align shifting
- rangeWindow simplified to rolling spans ending at now
- TransitionGraph "all" visual scale floored at the 30-day plot minimum

frontend/src/analytics/chart.js

@@ -1,8 +1,9 @@
 /**
  * Chart geometry, smoothing, and SVG path generation for analytics charts.
  *
- * Fixed 720x180 viewBox, stretched to the panel width; values are per-unit
- * rates (hour on the week view, day on month+).
+ * Fixed 720x180 plot area inside a larger viewBox that also holds the axis
+ * labels, so each chart SVG is self-contained; values are per-unit rates
+ * (hour on the week view, day on month+).
  */
 
 import { DAY, HOUR, MIN5, WEEK, mondayUTC } from './time.js'
@@ -11,6 +12,10 @@ import { formatCount } from './format.js'
 export const CHART_W = 720
 export const CHART_H = 180
 export const PAD_TOP = 14 // room above the highest point
+export const MARGIN_L = 56 // y tick labels + vertical axis label
+export const MARGIN_B = 24 // x tick labels
+export const VIEW_W = MARGIN_L + CHART_W + 8
+export const VIEW_H = CHART_H + MARGIN_B
 
 /**
  * Y always starts at 0; the max is a multiple of a 1-2-5 major step with at
@@ -190,7 +195,7 @@ export function buildChart(input, now = Date.now()) {
   const nMajor = Math.round(max / step)
   for (let k = 0; k <= nMajor; k++) {
     const v = k * step
-    majors.push({ value: v, y: y(v), bottom: (1 - PAD_TOP / CHART_H) * (v / max) * 100 })
+    majors.push({ value: v, y: y(v), label: fmtY(v) })
   }
   if (minor) {
     for (let v = minor; v < max; v += minor) {
@@ -204,37 +209,37 @@ export function buildChart(input, now = Date.now()) {
   // ranges: boundary lines at Mondays / months / years.
   const isWeek = t1 - t0 === WEEK
   const isMonth = !isWeek && t1 - t0 <= 31 * DAY
-  const xticks = isWeek
-    ? Array.from({ length: 7 }, (_, d) => {
-        const t = t0 + d * DAY + 12 * HOUR
-        return {
-          x: x(t), left: ((t - t0) / (t1 - t0)) * 100,
-          label: new Date(t).toLocaleDateString(undefined, {
-            weekday: 'short', timeZone: 'UTC',
-          }),
-          line: false,
-        }
+  let xticks
+  if (isWeek) {
+    xticks = Array.from({ length: 7 }, (_, d) => {
+      const t = t0 + d * DAY + 12 * HOUR
+      return {
+        x: x(t),
+        label: new Date(t).toLocaleDateString(undefined, {
+          weekday: 'short', timeZone: 'UTC',
+        }),
+        line: false,
+      }
+    })
+  } else if (isMonth) {
+    // t0 is day-aligned; label every day whose noon falls inside the range.
+    xticks = []
+    for (let day = t0; day + 12 * HOUR < t1; day += DAY) {
+      const date = new Date(day)
+      const t = day + 12 * HOUR
+      xticks.push({
+        x: x(t),
+        label: date.getUTCDate() === 1
+          ? date.toLocaleDateString(undefined, { month: 'short', timeZone: 'UTC' })
+          : String(date.getUTCDate()),
+        line: false,
       })
-    : isMonth
-      ? Array.from(
-          { length: Math.floor((t1 - Math.ceil(t0 / DAY) * DAY) / DAY) },
-          (_, d) => {
-            const day = Math.ceil(t0 / DAY) * DAY + d * DAY
-            const date = new Date(day)
-            const t = day + 12 * HOUR
-            return {
-              x: x(t), left: ((t - t0) / (t1 - t0)) * 100,
-              label: date.getUTCDate() === 1
-                ? date.toLocaleDateString(undefined, { month: 'short', timeZone: 'UTC' })
-                : String(date.getUTCDate()),
-              line: false,
-            }
-          },
-        )
-      : xticksFor(t0, t1).map((t) => ({
-          x: x(t), left: ((t - t0) / (t1 - t0)) * 100,
-          label: fmtTick(t, t1 - t0), line: true,
-        }))
+    }
+  } else {
+    xticks = xticksFor(t0, t1).map((t) => ({
+      x: x(t), label: fmtTick(t, t1 - t0), line: true,
+    }))
+  }
   return { max, majors, minors, series: drawn, xticks, unit }
 }
 
@@ -297,7 +302,7 @@ export function buildDayChart(input, now = Date.now()) {
   const nMajor = Math.round(max / step)
   for (let k = 0; k <= nMajor; k++) {
     const v = k * step
-    majors.push({ value: v, y: y(v), bottom: (1 - PAD_TOP / CHART_H) * (v / max) * 100 })
+    majors.push({ value: v, y: y(v), label: fmtY(v) })
   }
   if (minor) {
     for (let v = minor; v < max; v += minor) {
@@ -313,12 +318,10 @@ export function buildDayChart(input, now = Date.now()) {
     const d = new Date(t)
     xticks.push({
       x: ((t - t0) / (t1 - t0)) * CHART_W,
-      left: ((t - t0) / (t1 - t0)) * 100,
       label: `${String(d.getUTCHours()).padStart(2, '0')}:00`,
       line: false,
     })
   }
-
   return { bars, skyline: skyline.trim(), max, majors, minors, xticks, unit: '5min', series: [] }
 }
 

frontend/src/analytics/time.js

@@ -92,27 +92,38 @@ export function weeklySeries(buckets) {
  * to per-day rates (the unit the month+ charts are read in).
  * Ranges without a fixed span use the full data reach, but never less than
  * their configured minSpan so the chart keeps a readable minimum x scale.
+ * t0 is aligned to the UTC day so the x labels cover the whole range;
+ * t1 is now, so the scale never extends into the future. The bucket size
+ * follows the resulting window (6h up to 31 days, daily beyond), so ranges
+ * covering the same window — "all" at its 30-day minimum vs "month" —
+ * render the identical curve.
  */
 export function rollingSeries(buckets, rangeKey) {
   const raw = rawTimes(buckets)
   const times = Object.keys(raw).map(Number)
   if (!times.length) return null
   const { span, bucket, minSpan = 0 } = RANGES[rangeKey]
-  const t1 = Math.floor(Date.now() / bucket) * bucket + bucket
-  const earliest = Math.floor(Math.min(...times) / bucket) * bucket
-  const t0 = span != null
+  const t1 = Date.now()
+  const earliest = Math.min(...times)
+  const t0 = Math.floor((span != null
     ? t1 - span
-    : Math.min(earliest, t1 - minSpan)
+    : Math.min(earliest, t1 - minSpan)) / DAY) * DAY
+  // The bucket follows the actual window length, not the range key: when
+  // "all" is capped to its 30-day minimum it covers the very window "month"
+  // does, and daily bins would draw a different curve over the same data
+  // (coarser edge detection, points a day apart plotted at bin starts, the
+  // last point stuck at today's midnight instead of reaching now).
+  const bucketMs = t1 - t0 <= 31 * DAY ? Math.min(bucket, 6 * HOUR) : bucket
   const points = []
-  for (let t = t0; t < t1; t += bucket) {
-    points.push({ t, count: sumRange(raw, t, t + bucket) })
+  for (let t = t0; t < t1; t += bucketMs) {
+    points.push({ t, count: sumRange(raw, t, t + bucketMs) })
   }
   return {
     series: [{ points, label: '', opacity: 1, area: true }],
     t0,
     t1,
-    rate: DAY / bucket,
-    binMinutes: bucket / 60e3,
+    rate: DAY / bucketMs,
+    binMinutes: bucketMs / 60e3,
     unitMinutes: 24 * 60,
     unit: 'day',
   }
@@ -153,22 +164,19 @@ export function makeSeries(buckets, rangeKey) {
 /**
  * Absolute UTC time window for a given range key. Used to filter visits,
  * transitions and views for the non-chart stats on the analytics page.
- * The week range is a rolling 7 days ending at now; the charts instead
- * align to Monday 00:00 UTC and overlay previous weeks, so their x window
- * differs from the stats range on purpose.
+ * Every bounded range is a rolling span ending at now; the charts instead
+ * align week to Monday 00:00 UTC (overlaying previous weeks) and month+
+ * to UTC day boundaries, so their x windows differ from the stats range
+ * on purpose.
  * Returns { t0, t1 } where null means unbounded.
  */
 export function rangeWindow(rangeKey) {
   const now = Date.now()
-  if (rangeKey === 'week') {
-    return { t0: now - WEEK, t1: now }
-  }
   if (rangeKey === 'all') {
     return { t0: null, t1: null }
   }
-  const { span, bucket } = RANGES[rangeKey]
-  const t1 = Math.floor(now / bucket) * bucket + bucket
-  return { t0: t1 - span, t1 }
+  const span = rangeKey === 'week' ? WEEK : RANGES[rangeKey].span
+  return { t0: now - span, t1: now }
 }
 
 /**