feat: add Zero queries for all 6 synced tables

Define named queries matching each Electric hook's data needs:
- notifications.byUser (use-inbox)
- documents.bySpace (use-documents, use-documents-processing)
- connectors.bySpace (use-connectors-electric)
- messages.byThread (use-messages-electric)
- comments.byThread (use-comments-electric)
- chatSession.byThread (use-chat-session-state)

Also moves schema files from zero/tables/ to zero/schema/ for
consistent modular folder structure.

surfsense_web/zero/schema/chat.ts

@@ -0,0 +1,34 @@
+import { table, string, number, json } from "@rocicorp/zero";
+
+export const newChatMessageTable = table("new_chat_messages")
+	.columns({
+		id: number(),
+		role: string(),
+		content: json(),
+		threadId: number().from("thread_id"),
+		authorId: string().optional().from("author_id"),
+		createdAt: number().from("created_at"),
+	})
+	.primaryKey("id");
+
+export const chatCommentTable = table("chat_comments")
+	.columns({
+		id: number(),
+		messageId: number().from("message_id"),
+		threadId: number().from("thread_id"),
+		parentId: number().optional().from("parent_id"),
+		authorId: string().optional().from("author_id"),
+		content: string(),
+		createdAt: number().from("created_at"),
+		updatedAt: number().from("updated_at"),
+	})
+	.primaryKey("id");
+
+export const chatSessionStateTable = table("chat_session_state")
+	.columns({
+		id: number(),
+		threadId: number().from("thread_id"),
+		aiRespondingToUserId: string().optional().from("ai_responding_to_user_id"),
+		updatedAt: number().from("updated_at"),
+	})
+	.primaryKey("id");