feat: bitwise RBAC engine with channel-level permission overrides

Replace string-based role checks (role === 'admin') with a bitwise BigInt
permission system. Adds computePermissions() resolution engine following
Discord's model: @everyone base → role union → admin shortcut → channel
overrides (role deny/allow → member deny/allow). Ready payload now filters
channels by VIEW_CHANNEL and attaches per-user myPermissions to each
server and channel. Includes channel_overrides table, @everyone role
auto-creation, migration for existing servers, and override CRUD API.

packages/server/src/db/seed.ts

@@ -2,6 +2,7 @@ import { getDb, schema } from './index.js';
 import { generateSnowflake } from '../utils/snowflake.js';
 import { hashPassword } from '../utils/auth.js';
 import { eq } from 'drizzle-orm';
+import { DEFAULT_EVERYONE_PERMISSIONS, permissionsToString } from '@opencord/shared/src/permissions.js';
 
 export async function seedDatabase(): Promise<void> {
   const db = getDb();
@@ -63,6 +64,17 @@ export async function seedDatabase(): Promise<void> {
     createdAt: Date.now(),
   }).run();
 
+  // Create @everyone role (id === serverId convention)
+  db.insert(schema.roles).values({
+    id: serverId,
+    serverId: serverId,
+    name: '@everyone',
+    color: '#b9bbbe',
+    position: 0,
+    permissions: permissionsToString(DEFAULT_EVERYONE_PERMISSIONS),
+    createdAt: Date.now(),
+  }).run();
+
   console.log('Database seeded successfully');
   console.log(`  Default server: Opencord (invite code: opencord)`);
   console.log(`  Admin user: admin / admin123`);