fix(charts): align every chart tooltip on the borderless soft-shadow card

One visual contract for all three D3 tooltip surfaces, matching the
design reference: p-4, rounded-2xl, shadow-xl, no edge ring in light
mode. Dark mode keeps a 1px alpha-white ring since a shadow alone
disappears against dark surfaces.

- goal_projection_chart_controller drops its hand-copied class string
  (it still carried the old bordered recipe — the drift this util
  exists to prevent) and builds its two lines through the shared
  factory: secondary date line, tabular value line.
- New content conventions exported alongside the container contract:
  context line = text-xs text-secondary, values = font-medium
  tabular-nums. Time-series and sankey adopt them.
- Sankey node titles now escape before .html(); user-named categories
  were previously interpolated raw into the tooltip markup.

app/javascript/controllers/time_series_chart_controller.js

@@ -385,11 +385,11 @@ export default class extends Controller {
 
   _tooltipTemplate(datum) {
     return `
-      <div style="margin-bottom: 4px; color: var(--color-gray-500);">
+      <div class="text-xs text-secondary mb-1">
         ${datum.date_formatted}
       </div>
       <div class="flex items-center gap-4">
-        <div class="flex items-center gap-2 text-primary">
+        <div class="flex items-center gap-2 text-primary font-medium tabular-nums">
           <div class="flex items-center justify-center h-4 w-4">
             ${this._getTrendIcon(datum)}
           </div>
@@ -400,7 +400,7 @@ export default class extends Controller {
           datum.trend.value === 0
             ? `<span class="w-20"></span>`
             : `
-          <span style="color: ${datum.trend.color};">
+          <span class="tabular-nums" style="color: ${datum.trend.color};">
             ${this._extractFormattedValue(datum.trend.value)} (${datum.trend.percent_formatted})
           </span>
         `