Add multi-guild Discord OAuth support

- Users can now login via Bacanaks OR Piccadilly Discord server
- Highest role from all servers is used (superadmin > moderator > user)
- Lazy initialization fixes env loading timing issue
- Updated documentation with implementation details and troubleshooting

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

discord.js

@@ -1,6 +1,29 @@
 // Discord OAuth2 Service
 const DISCORD_API = 'https://discord.com/api/v10';
 
+// Lazy initialization - wird erst bei Verwendung geladen (nach dotenv)
+let _guildConfigs = null;
+
+function getGuildConfigs() {
+  if (_guildConfigs === null) {
+    _guildConfigs = [
+      {
+        name: 'Bacanaks',
+        guildId: process.env.DISCORD_GUILD_ID_1,
+        adminRoleId: process.env.DISCORD_ADMIN_ROLE_ID_1,
+        modRoleId: process.env.DISCORD_MOD_ROLE_ID_1
+      },
+      {
+        name: 'Piccadilly',
+        guildId: process.env.DISCORD_GUILD_ID_2,
+        adminRoleId: process.env.DISCORD_ADMIN_ROLE_ID_2,
+        modRoleId: process.env.DISCORD_MOD_ROLE_ID_2
+      }
+    ].filter(config => config.guildId);
+  }
+  return _guildConfigs;
+}
+
 export function getDiscordAuthUrl() {
   const params = new URLSearchParams({
     client_id: process.env.DISCORD_CLIENT_ID,
@@ -48,9 +71,10 @@ export async function getDiscordUser(accessToken) {
   return response.json();
 }
 
-export async function getGuildMember(userId) {
+// Prüft einen einzelnen Server
+async function fetchGuildMember(guildId, userId) {
   const response = await fetch(
-    `${DISCORD_API}/guilds/${process.env.DISCORD_GUILD_ID}/members/${userId}`,
+    `${DISCORD_API}/guilds/${guildId}/members/${userId}`,
     {
       headers: {
         Authorization: `Bot ${process.env.DISCORD_BOT_TOKEN}`
@@ -60,17 +84,78 @@ export async function getGuildMember(userId) {
 
   if (!response.ok) {
     if (response.status === 404) {
-      return null; // User not in guild
+      return null;
     }
-    throw new Error('Failed to get guild member');
+    throw new Error(`Failed to get guild member from ${guildId}`);
   }
 
   return response.json();
 }
 
+// Prüft alle konfigurierten Server und gibt Memberships zurück
+export async function getGuildMemberships(userId) {
+  const configs = getGuildConfigs();
+  const memberships = [];
+
+  for (const config of configs) {
+    try {
+      const member = await fetchGuildMember(config.guildId, userId);
+      if (member) {
+        memberships.push({
+          config,
+          member,
+          roles: member.roles || []
+        });
+      }
+    } catch (err) {
+      console.error(`[Discord] Failed to check membership for guild ${config.name}:`, err.message);
+    }
+  }
+
+  return memberships.length > 0 ? memberships : null;
+}
+
+// Legacy-Funktion für Kompatibilität
+export async function getGuildMember(userId) {
+  const memberships = await getGuildMemberships(userId);
+  if (!memberships || memberships.length === 0) {
+    return null;
+  }
+  return memberships[0].member;
+}
+
+// Rollen-Priorität: superadmin > moderator > user
+const ROLE_PRIORITY = { superadmin: 3, moderator: 2, user: 1 };
+
+// Bestimmt die höchste Rolle aus allen Server-Memberships
+export function getUserRoleFromMemberships(memberships) {
+  if (!memberships || memberships.length === 0) {
+    return 'user';
+  }
+
+  let highestRole = 'user';
+
+  for (const { config, roles } of memberships) {
+    let role = 'user';
+
+    if (roles.includes(config.adminRoleId)) {
+      role = 'superadmin';
+    } else if (roles.includes(config.modRoleId)) {
+      role = 'moderator';
+    }
+
+    if (ROLE_PRIORITY[role] > ROLE_PRIORITY[highestRole]) {
+      highestRole = role;
+    }
+  }
+
+  return highestRole;
+}
+
+// Legacy-Funktion für Kompatibilität
 export function getUserRole(memberRoles) {
-  const adminRoleId = process.env.DISCORD_ADMIN_ROLE_ID;
-  const modRoleId = process.env.DISCORD_MOD_ROLE_ID;
+  const adminRoleId = process.env.DISCORD_ADMIN_ROLE_ID || process.env.DISCORD_ADMIN_ROLE_ID_1;
+  const modRoleId = process.env.DISCORD_MOD_ROLE_ID || process.env.DISCORD_MOD_ROLE_ID_1;
 
   if (memberRoles.includes(adminRoleId)) {
     return 'superadmin';