fix(dashboard): infinite scroll, auto-refetch, analytics cache invalidation, remove topic row cap

Frontend:
- Cursor pagination (100/page) replacing hardcoded 80 message limit
- Removed .slice(0,200) cap on mergeMessages
- IntersectionObserver infinite scroll with skeleton loading
- 15s periodic refetch for message list sync

Backend:
- Removed LIMIT 2000 from topic trends SQL query
- Added invalidateAnalyticsCache on message capture (messageCreated)
- Added invalidateAnalyticsCache on batch analysis completion

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/moderation/aiAnalyzer.ts

@@ -21,6 +21,7 @@ import {
   updateMessageAIAnalysis,
   updateMessagesAIAnalysisBulk,
 } from "./messageStore.js";
+import { invalidateAnalyticsCache } from "./analyticsStore.js";
 import type {
   AnalysisQueueStatus,
   MessageRecord,
@@ -374,6 +375,7 @@ async function processIndividualFallback(
     const rows = await updateMessagesAIAnalysisBulk(updates);
     for (const row of rows) {
       getModerationBroadcaster()?.messageAnalyzed(row);
+      invalidateAnalyticsCache(row.guild_id);
       scheduleAutoDelete(row);
     }
 

src/moderation/analyticsStore.ts

@@ -424,8 +424,8 @@ export async function getTopicTrends(input: {
   try {
     const since = Date.now() - hours * 3600_000;
 
-    // Only fetch messages that have ai_analysis (the ones that actually have topics)
-    // This dramatically reduces rows for large guilds
+    // Fetch all analyzed messages within the time window (no hard row cap).
+    // Messages without ai_analysis are excluded which naturally limits rows.
     const rows = (await executeAll(
       `
       SELECT
@@ -438,7 +438,6 @@ export async function getTopicTrends(input: {
         AND ai_analysis IS NOT NULL
         ${channelId ? `AND (channel_id = ? OR thread_id = ?)` : ""}
       ORDER BY created_at DESC
-      LIMIT 2000
       `,
       channelId ? [guildId, since, channelId, channelId] : [guildId, since],
     )) as MessageRecord[];

src/moderation/messageCapture.ts

@@ -16,6 +16,7 @@ import {
   updateMessageAsEdited,
   upsertMessageForCapture,
 } from "./messageStore.js";
+import { invalidateAnalyticsCache } from "./analyticsStore.js";
 import type { AttachmentRecord, MessageRecord } from "./types.js";
 
 const logger = createChildLogger("message-capture");
@@ -127,6 +128,9 @@ export async function captureMessage(
     broadcaster.messageCreated(messageRecord);
   }
 
+  // Invalidate analytics cache so real-time stats reflect the new message
+  invalidateAnalyticsCache(messageRecord.guild_id);
+
   const attachmentUploadTasks: Promise<void>[] = [];
 
   // Insert attachments before queuing analysis to avoid race condition