feat(phase6a): behavioral insight pipeline ingestion + tagging + compression

- prisma: sessions_meta, compressed_sessions, ingestion_watermarks
- worker: PostHog client (eu.i.posthog.com), heuristic filter
- worker: BullMQ insight-pipeline queue (ingest 5min / tag 2min / compress 3min)
- worker: tagger (bug_suspected, ux_friction, upgrade_hesitation, etc.) + severity scoring
- worker: rrweb -> semantic timeline transform + 8-pattern PII sanitization
- worker: fingerprint hash + MinIO upload (bucket: insight-compressed)
- web: /insights pipeline dashboard + session timeline viewer
- sidebar: Insights nav entry

LLM (Phase 6b), insight inbox, cost dashboard, GitHub loop deferred to later phases.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

apps/web/prisma/schema.prisma

@@ -110,3 +110,69 @@ model AuditLog {
   @@index([actorUserId])
   @@index([projectKey])
 }
+
+// ---------- Phase 6a: Behavioral Insight Pipeline ----------
+
+model SessionMeta {
+  id                String   @id
+  projectKey        String
+  userIdHash        String?
+  isAuthenticated   Boolean  @default(false)
+  subscriptionTier  String?
+  startedAt         DateTime
+  durationMs        Int
+  pageviewCount     Int      @default(0)
+  clickCount        Int      @default(0)
+  errorCount        Int      @default(0)
+  rageClickCount    Int      @default(0)
+  deadClickCount    Int      @default(0)
+  network5xxCount   Int      @default(0)
+  network4xxCount   Int      @default(0)
+  startUrl          String?
+  promotionReasons  String[]
+  tags              String[]
+  severity          String?
+  score             Int?
+  rawMetadataUrl    String?
+  status            String   @default("pending_signal")
+  fingerprint       String?
+  processedAt       DateTime?
+  createdAt         DateTime @default(now())
+
+  compressed        CompressedSession?
+
+  @@index([status, createdAt])
+  @@index([fingerprint])
+  @@index([projectKey, status])
+  @@index([userIdHash, startedAt])
+  @@map("sessions_meta")
+}
+
+model CompressedSession {
+  sessionId                String   @id
+  fingerprint              String
+  semanticTimelineMinioKey String
+  tokenCountInput          Int
+  tokenCountEstOutput      Int
+  compressionRatio         Float?
+  sanitizationMatchCount   Int      @default(0)
+  sanitizationBreakdown    Json?
+  isBundle                 Boolean  @default(false)
+  bundleSessionIds         String[]
+  readyForAnalysisAt       DateTime @default(now())
+  createdAt                DateTime @default(now())
+
+  session SessionMeta @relation(fields: [sessionId], references: [id], onDelete: Cascade)
+
+  @@index([fingerprint])
+  @@map("compressed_sessions")
+}
+
+model IngestionWatermark {
+  projectKey     String   @id
+  lastPolledAt   DateTime
+  posthogCursor  String?
+  updatedAt      DateTime @updatedAt
+
+  @@map("ingestion_watermarks")
+}