feat: add weather trend chart showing indicator averages over time

Adds a collapsible SVG line graph on weather session pages displaying
the evolution of all 4 indicators (Performance, Moral, Flux, Création
de valeur) across sessions, with per-session average scores, hover
tooltips, and a marker on the current session.

Also fixes pre-existing lint errors: non-null assertion on optional
chain in Header and eslint-disable for intentional hydration pattern
in ThemeToggle.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/weather/[id]/page.tsx

@@ -2,13 +2,18 @@ import { notFound } from 'next/navigation';
 import Link from 'next/link';
 import { auth } from '@/lib/auth';
 import { getWorkshop, getSessionsTabUrl } from '@/lib/workshops';
-import { getWeatherSessionById, getPreviousWeatherEntriesForUsers } from '@/services/weather';
+import {
+  getWeatherSessionById,
+  getPreviousWeatherEntriesForUsers,
+  getWeatherSessionsHistory,
+} from '@/services/weather';
 import { getUserTeams } from '@/services/teams';
 import {
   WeatherBoard,
   WeatherLiveWrapper,
   WeatherInfoPanel,
   WeatherAverageBar,
+  WeatherTrendChart,
 } from '@/components/weather';
 import { Badge } from '@/components/ui';
 import { EditableWeatherTitle } from '@/components/ui/EditableWeatherTitle';
@@ -33,9 +38,10 @@ export default async function WeatherSessionPage({ params }: WeatherSessionPageP
 
   const allUserIds = [session.user.id, ...session.shares.map((s: { userId: string }) => s.userId)];
 
-  const [previousEntries, userTeams] = await Promise.all([
+  const [previousEntries, userTeams, history] = await Promise.all([
     getPreviousWeatherEntriesForUsers(session.id, session.date, allUserIds),
     getUserTeams(authSession.user.id),
+    getWeatherSessionsHistory(authSession.user.id),
   ]);
 
   return (
@@ -79,6 +85,9 @@ export default async function WeatherSessionPage({ params }: WeatherSessionPageP
       {/* Info sur les catégories */}
       <WeatherInfoPanel />
 
+      {/* Évolution dans le temps */}
+      <WeatherTrendChart data={history} currentSessionId={session.id} />
+
       {/* Live Wrapper + Board */}
       <WeatherLiveWrapper
         sessionId={session.id}