feat: enhance textbook reader with anchor text support and improve knowledge point management

src/shared/db/schema.ts

@@ -118,6 +118,7 @@ export const knowledgePoints = mysqlTable("knowledge_points", {
   id: id("id").primaryKey(),
   name: varchar("name", { length: 255 }).notNull(),
   description: text("description"),
+  anchorText: varchar("anchor_text", { length: 255 }),
   
   // Tree Structure: Parent KP
   parentId: varchar("parent_id", { length: 128 }), // Self-reference defined in relations