profile-weekly-distance: weekly distance bar chart on the profile

Implements the profile-weekly-distance change (specs/profile-weekly-distance):

- getWeeklyDistance(ownerId, { publicOnly, weeks=12 }) in activities.server.ts:
  one query that gap-fills in SQL — generate_series of week-starts LEFT JOINed
  to activities — so it returns exactly 12 contiguous { weekStart, distance }
  rows with matching Postgres week boundaries, viewer-scoped, no cache, no
  schema change.
- WeeklyDistanceChart: SVG bars normalized to the busiest week (empty weeks keep
  their slot as zero-height bars), per-bar title distance, localized label;
  renders nothing when there's no distance in the window. Mounted under the
  ProfileStats header.
- i18n journal.profileStats.weeklyDistance (en + de).

Tests: WeeklyDistanceChart component (jsdom: bar count incl. zero weeks, empty
→ hidden, normalization); e2e creates an activity with distance and asserts the
chart renders. typecheck + lint + unit (journal 321) green; verified in the
browser.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

packages/i18n/src/locales/de.ts

@@ -415,6 +415,7 @@ export default {
       ascent: "Anstieg",
       time: "Zeit",
       last4Weeks: "{{count}} in den letzten 4 Wochen",
+      weeklyDistance: "Wochendistanz (letzte 12 Wochen)",
     },
     settings: {
       title: "Einstellungen",

packages/i18n/src/locales/en.ts

@@ -415,6 +415,7 @@ export default {
       ascent: "Ascent",
       time: "Time",
       last4Weeks: "{{count}} in the last 4 weeks",
+      weeklyDistance: "Weekly distance (last 12 weeks)",
     },
     settings: {
       title: "Settings",