Fix title-race chart: persist the diary, dedupe restarts, date axis

The chart looked broken because its data was: history lived in memory,
so every deploy wiped it (yesterday's points were gone), and each boot
plus the +5min refit appended a fresh point labeled with the same last
result — leaving two identical flat segments on an index axis.

- model_history table: every diary point persists with the finished-
  result signature it was computed from; restored at boot
- points only append when the finished set actually changes — refit
  and boot recomputes update the snapshot without spamming the diary
- one-time rebuild when nothing is persisted: replay finished results
  in kickoff order, re-running the sim after each with later results
  masked, so the historical points are recreated faithfully
- chart x-axis shows localized dates instead of raw indices

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/components/OddsChart.tsx

@@ -1,6 +1,7 @@
 import { useMemo } from 'react';
 import { LineChart, Line, XAxis, YAxis, Tooltip, ResponsiveContainer, CartesianGrid, Legend } from 'recharts';
 import { teamFlag } from '@/lib/teams';
+import { useFormat } from '@/lib/i18n';
 import type { OddsHistoryPoint } from '@/lib/types';
 
 const PALETTE = [
@@ -15,23 +16,32 @@ const PALETTE = [
 /** Championship odds over time — one line per top contender, a point per result
  *  that moved the model. */
 export function OddsChart({ history }: { history: OddsHistoryPoint[] }) {
+  const { locale } = useFormat();
   const { data, teams } = useMemo(() => {
     const last = history[history.length - 1];
     const teams = (last?.top ?? []).slice(0, 6).map((t) => t.team);
+    const tag = locale === 'de' ? 'de-DE' : 'en-GB';
     const data = history.map((h, i) => {
-      const row: Record<string, number | string> = { i: i + 1, label: h.label };
+      const day = new Date(h.t).toLocaleDateString(tag, { day: 'numeric', month: 'short' });
+      const row: Record<string, number | string> = { i: i + 1, label: h.label, day };
       for (const t of h.top) if (teams.includes(t.team)) row[t.team] = Math.round(t.champion * 1000) / 10;
       return row;
     });
     return { data, teams };
-  }, [history]);
+  }, [history, locale]);
 
   return (
     <div className="h-72 w-full">
       <ResponsiveContainer width="100%" height="100%">
         <LineChart data={data} margin={{ top: 8, right: 16, bottom: 4, left: -8 }}>
           <CartesianGrid stroke="var(--app-line)" strokeDasharray="3 3" vertical={false} />
-          <XAxis dataKey="i" tick={{ fill: 'var(--app-faint)', fontSize: 11 }} stroke="var(--app-line)" />
+          <XAxis
+            dataKey="i"
+            tick={{ fill: 'var(--app-faint)', fontSize: 11 }}
+            stroke="var(--app-line)"
+            tickFormatter={(i) => String(data[Number(i) - 1]?.day ?? '')}
+            minTickGap={28}
+          />
           <YAxis
             tick={{ fill: 'var(--app-faint)', fontSize: 11 }}
             stroke="var(--app-line)"