chore: update postgresql.conf and contracts comments for Zero

- Replace Electric SQL references in postgresql.conf with Zero-cache
- Clean Electric SQL comments in chat-comments.types.ts and chat-messages.types.ts

surfsense_web/contracts/types/chat-comments.types.ts

@@ -6,7 +6,7 @@ import { z } from "zod";
 export const rawComment = z.object({
 	id: z.number(),
 	message_id: z.number(),
-	thread_id: z.number(), // Denormalized for efficient Electric subscriptions
+	thread_id: z.number(), // Denormalized for efficient per-thread sync
 	parent_id: z.number().nullable(),
 	author_id: z.string().nullable(),
 	content: z.string(),

surfsense_web/contracts/types/chat-messages.types.ts

@@ -1,7 +1,7 @@
 import { z } from "zod";
 
 /**
- * Raw message from database (Electric SQL sync)
+ * Raw message from database (real-time sync)
  */
 export const rawMessage = z.object({
 	id: z.number(),