feat: Implement core chat page with channel navigation, direct messages, and voice chat integration.

convex/schema.ts

@@ -18,13 +18,19 @@ export default defineSchema({
     customStatus: v.optional(v.string()),
   }).index("by_username", ["username"]),
 
+  categories: defineTable({
+    name: v.string(),
+    position: v.number(),
+  }).index("by_position", ["position"]),
+
   channels: defineTable({
     name: v.string(),
     type: v.string(), // 'text' | 'voice' | 'dm'
-    category: v.optional(v.string()),
+    categoryId: v.optional(v.id("categories")),
     topic: v.optional(v.string()),
     position: v.optional(v.number()),
-  }).index("by_name", ["name"]),
+  }).index("by_name", ["name"])
+    .index("by_category", ["categoryId"]),
 
   messages: defineTable({
     channelId: v.id("channels"),