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/documents.ts

@@ -0,0 +1,31 @@
+import { table, string, number, boolean, json } from "@rocicorp/zero";
+
+export const documentTable = table("documents")
+	.columns({
+		id: number(),
+		title: string(),
+		documentType: string().from("document_type"),
+		searchSpaceId: number().from("search_space_id"),
+		createdById: string().optional().from("created_by_id"),
+		status: json(),
+		createdAt: number().from("created_at"),
+	})
+	.primaryKey("id");
+
+export const searchSourceConnectorTable = table("search_source_connectors")
+	.columns({
+		id: number(),
+		name: string(),
+		connectorType: string().from("connector_type"),
+		isIndexable: boolean().from("is_indexable"),
+		lastIndexedAt: number().optional().from("last_indexed_at"),
+		config: json(),
+		enableSummary: boolean().from("enable_summary"),
+		periodicIndexingEnabled: boolean().from("periodic_indexing_enabled"),
+		indexingFrequencyMinutes: number().optional().from("indexing_frequency_minutes"),
+		nextScheduledAt: number().optional().from("next_scheduled_at"),
+		searchSpaceId: number().from("search_space_id"),
+		userId: string().from("user_id"),
+		createdAt: number().from("created_at"),
+	})
+	.primaryKey("id");