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>

playwright.config.ts

@@ -146,6 +146,14 @@ export default defineConfig({
         baseURL: "http://localhost:3000",
       },
     },
+    {
+      name: "profile-weekly-distance",
+      testMatch: "profile-weekly-distance.test.ts",
+      use: {
+        ...devices["Desktop Chrome"],
+        baseURL: "http://localhost:3000",
+      },
+    },
   ],
   webServer: process.env.CI
     ? [