fix: use cookie-based storage for Supabase client auth

Store auth session in cookies instead of localStorage so server-side
code (admin layout, API routes, protected layout) can read the session.
Implements chunked cookie support for large session tokens.

https://claude.ai/code/session_01H2aRGDaKgarPvhay2HxN6Y

lib/supabase/client.ts

@@ -1,9 +1,74 @@
 import { createClient as createSupabaseClient } from "@supabase/supabase-js";
 import type { Database } from "@/types/database.types";
 
-// Client Supabase côté navigateur (composants client)
+// Storage basé sur les cookies pour que le serveur puisse lire la session
+// Remplace le localStorage par défaut de Supabase
+const cookieStorage = {
+  getItem: (key: string): string | null => {
+    if (typeof document === "undefined") return null;
+
+    // Essayer le cookie direct
+    const escaped = key.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
+    const match = document.cookie.match(
+      new RegExp(`(?:^|; )${escaped}=([^;]*)`)
+    );
+    if (match) return decodeURIComponent(match[1]);
+
+    // Essayer les cookies chunked (.0, .1, .2, ...)
+    const chunks: string[] = [];
+    for (let i = 0; i < 10; i++) {
+      const chunkMatch = document.cookie.match(
+        new RegExp(`(?:^|; )${escaped}\\.${i}=([^;]*)`)
+      );
+      if (chunkMatch) {
+        chunks.push(decodeURIComponent(chunkMatch[1]));
+      } else {
+        break;
+      }
+    }
+    if (chunks.length > 0) return chunks.join("");
+
+    return null;
+  },
+
+  setItem: (key: string, value: string): void => {
+    if (typeof document === "undefined") return;
+
+    // Supprimer les anciens cookies d'abord
+    cookieStorage.removeItem(key);
+
+    const maxChunkSize = 3500; // Limite cookie ~4KB avec overhead
+
+    if (value.length <= maxChunkSize) {
+      document.cookie = `${key}=${encodeURIComponent(value)}; path=/; max-age=${60 * 60 * 24 * 365}; SameSite=Lax`;
+    } else {
+      // Découper en chunks
+      for (let i = 0; i * maxChunkSize < value.length; i++) {
+        const chunk = value.substring(i * maxChunkSize, (i + 1) * maxChunkSize);
+        document.cookie = `${key}.${i}=${encodeURIComponent(chunk)}; path=/; max-age=${60 * 60 * 24 * 365}; SameSite=Lax`;
+      }
+    }
+  },
+
+  removeItem: (key: string): void => {
+    if (typeof document === "undefined") return;
+    document.cookie = `${key}=; path=/; max-age=0`;
+    for (let i = 0; i < 10; i++) {
+      document.cookie = `${key}.${i}=; path=/; max-age=0`;
+    }
+  },
+};
+
+// Client Supabase côté navigateur
+// Utilise les cookies comme storage pour que le serveur puisse lire la session
 export const createClient = () =>
   createSupabaseClient<Database>(
     process.env.NEXT_PUBLIC_SUPABASE_URL!,
-    process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!
+    process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!,
+    {
+      auth: {
+        storage: cookieStorage,
+        flowType: "pkce",
+      },
+    }
   );