Implement Dashboard page with real data integration (P1.7)

Wire up the Dashboard page with /api/today data:
- Fetch today's decision, biometrics, and nutrition on mount
- Display DecisionCard with status, icon, and reason
- Show DataPanel with HRV, Body Battery, intensity minutes
- Show NutritionPanel with seed cycling and carb guidance
- Integrate OverrideToggles with POST/DELETE /api/overrides
- Handle loading states, error states, and setup prompts
- Display cycle day and phase information

Add 23 unit tests for the Dashboard component covering:
- Data fetching from /api/today and /api/user
- Component rendering (DecisionCard, DataPanel, NutritionPanel)
- Override toggle functionality (POST/DELETE API calls)
- Error handling and loading states
- Cycle information display

Also fixed TypeScript error in login page tests (resolveAuth
initialization).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/app/page.tsx

@@ -1,6 +1,129 @@
 // ABOUTME: Main dashboard page for PhaseFlow.
 // ABOUTME: Displays today's training decision, biometrics, and quick actions.
+"use client";
+
+import { useCallback, useEffect, useState } from "react";
+
+import { DataPanel } from "@/components/dashboard/data-panel";
+import { DecisionCard } from "@/components/dashboard/decision-card";
+import { NutritionPanel } from "@/components/dashboard/nutrition-panel";
+import { OverrideToggles } from "@/components/dashboard/override-toggles";
+import type {
+  CyclePhase,
+  Decision,
+  NutritionGuidance,
+  OverrideType,
+  PhaseConfig,
+} from "@/types";
+
+interface TodayData {
+  decision: Decision;
+  cycleDay: number;
+  phase: CyclePhase;
+  phaseConfig: PhaseConfig;
+  daysUntilNextPhase: number;
+  cycleLength: number;
+  biometrics: {
+    hrvStatus: string;
+    bodyBatteryCurrent: number;
+    bodyBatteryYesterdayLow: number;
+    weekIntensityMinutes: number;
+    phaseLimit: number;
+  };
+  nutrition: NutritionGuidance;
+}
+
+interface UserData {
+  id: string;
+  email: string;
+  activeOverrides: OverrideType[];
+}
+
 export default function Dashboard() {
+  const [todayData, setTodayData] = useState<TodayData | null>(null);
+  const [userData, setUserData] = useState<UserData | null>(null);
+  const [loading, setLoading] = useState(true);
+  const [error, setError] = useState<string | null>(null);
+
+  const fetchTodayData = useCallback(async () => {
+    const response = await fetch("/api/today");
+    const data = await response.json();
+
+    if (!response.ok) {
+      throw new Error(data.error || "Failed to fetch today data");
+    }
+
+    return data as TodayData;
+  }, []);
+
+  const fetchUserData = useCallback(async () => {
+    const response = await fetch("/api/user");
+    const data = await response.json();
+
+    if (!response.ok) {
+      throw new Error(data.error || "Failed to fetch user data");
+    }
+
+    return data as UserData;
+  }, []);
+
+  useEffect(() => {
+    async function loadData() {
+      try {
+        setLoading(true);
+        setError(null);
+
+        const [today, user] = await Promise.all([
+          fetchTodayData(),
+          fetchUserData(),
+        ]);
+
+        setTodayData(today);
+        setUserData(user);
+      } catch (err) {
+        setError(err instanceof Error ? err.message : "An error occurred");
+      } finally {
+        setLoading(false);
+      }
+    }
+
+    loadData();
+  }, [fetchTodayData, fetchUserData]);
+
+  const handleOverrideToggle = async (override: OverrideType) => {
+    if (!userData) return;
+
+    const isActive = userData.activeOverrides.includes(override);
+    const method = isActive ? "DELETE" : "POST";
+
+    try {
+      const response = await fetch("/api/overrides", {
+        method,
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({ override }),
+      });
+
+      if (!response.ok) {
+        throw new Error("Failed to update override");
+      }
+
+      const result = await response.json();
+
+      // Update local state with new overrides
+      setUserData((prev) =>
+        prev ? { ...prev, activeOverrides: result.activeOverrides } : null,
+      );
+
+      // Refetch today data to get updated decision
+      const newTodayData = await fetchTodayData();
+      setTodayData(newTodayData);
+    } catch (err) {
+      setError(
+        err instanceof Error ? err.message : "Failed to toggle override",
+      );
+    }
+  };
+
   return (
     <div className="min-h-screen bg-zinc-50 dark:bg-black">
       <header className="border-b bg-white dark:bg-zinc-900 px-6 py-4">
@@ -16,12 +139,63 @@ export default function Dashboard() {
       </header>
 
       <main className="container mx-auto p-6">
-        <div className="text-center py-12">
-          <p className="text-zinc-500">Dashboard placeholder</p>
-          <p className="text-sm text-zinc-400 mt-2">
-            Connect your Garmin and set your period date to get started.
-          </p>
-        </div>
+        {loading && (
+          <div className="text-center py-12">
+            <p className="text-zinc-500">Loading...</p>
+          </div>
+        )}
+
+        {error && (
+          <div role="alert" className="text-center py-12">
+            <p className="text-red-500">Error: {error}</p>
+            {error.includes("lastPeriodDate") && (
+              <p className="text-sm text-zinc-400 mt-2">
+                Please log your period start date to get started.
+              </p>
+            )}
+          </div>
+        )}
+
+        {!loading && !error && todayData && userData && (
+          <div className="space-y-6">
+            {/* Cycle Info */}
+            <div className="text-center">
+              <p className="text-lg font-medium">
+                Day {todayData.cycleDay} · {todayData.phase}
+              </p>
+              <p className="text-sm text-zinc-500">
+                {todayData.daysUntilNextPhase} days until next phase
+              </p>
+            </div>
+
+            {/* Decision Card */}
+            <DecisionCard decision={todayData.decision} />
+
+            {/* Data and Nutrition Grid */}
+            <div className="grid gap-4 md:grid-cols-2">
+              <DataPanel
+                bodyBatteryCurrent={todayData.biometrics.bodyBatteryCurrent}
+                bodyBatteryYesterdayLow={
+                  todayData.biometrics.bodyBatteryYesterdayLow
+                }
+                hrvStatus={todayData.biometrics.hrvStatus}
+                weekIntensity={todayData.biometrics.weekIntensityMinutes}
+                phaseLimit={todayData.biometrics.phaseLimit}
+                remainingMinutes={
+                  todayData.biometrics.phaseLimit -
+                  todayData.biometrics.weekIntensityMinutes
+                }
+              />
+              <NutritionPanel nutrition={todayData.nutrition} />
+            </div>
+
+            {/* Override Toggles */}
+            <OverrideToggles
+              activeOverrides={userData.activeOverrides}
+              onToggle={handleOverrideToggle}
+            />
+          </div>
+        )}
       </main>
     </div>
   );