feat: member portal Sprint 6 — Seva + multi-signal gamification

- SevaOpportunity + SevaEntry + GamificationEvent models + migration
- GamificationService: multi-signal point table (helpful answer +10, seva +20,
  event +5, FAQ +15, welcome +3, profile +5, business +5), idempotent award via
  unique(userId,type,refId), lifetime + time-decayed "recent" score, leaderboard
- SevaModule: admin CRUD + mark-entry-complete (awards SEVA_COMPLETED points)
- Member endpoints in MyController: GET /my/seva, POST /my/seva/:id/signup|cancel
- PROFILE_COMPLETED auto-awarded on profile update (name+hometown+interest)
- /my/seva page: points hero with per-type breakdown, open opportunities w/ signup,
  leaderboard (respects directoryVisible), my seva history
- Member + admin BFF routes; Seva & Points nav item
- Register GamificationModule + SevaModule; add SEVA_* audit actions

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/api/prisma/schema.prisma

@@ -92,6 +92,8 @@ model Tenant {
   digests        Digest[]
   events         Event[]
   threads        Thread[]
+  sevaOpportunities  SevaOpportunity[]
+  gamificationEvents GamificationEvent[]
 }
 
 enum AdminRole {
@@ -416,6 +418,8 @@ model TowerUser {
   sessions TowerSession[]
   messages Message[]      @relation("senderTowerUser")
   rsvps    EventRsvp[]
+  sevaEntries        SevaEntry[]
+  gamificationEvents GamificationEvent[]
 
   @@unique([tenantId, phoneHash])
   @@index([phoneHash])
@@ -602,3 +606,86 @@ model EventRsvp {
   @@unique([eventId, userId])
   @@index([userId])
 }
+
+// ============================================================================
+// Seva (volunteering) + Gamification
+// ============================================================================
+
+enum SevaStatus {
+  OPEN
+  CLOSED
+}
+
+enum SevaEntryStatus {
+  SIGNED_UP
+  COMPLETED
+  CANCELLED
+}
+
+model SevaOpportunity {
+  id          String     @id @default(cuid())
+  tenantId    String
+  tenant      Tenant     @relation(fields: [tenantId], references: [id])
+  title       String
+  description String?
+  location    String?
+  slots       Int?
+  startsAt    DateTime?
+  pointsAward Int        @default(20)
+  status      SevaStatus @default(OPEN)
+  createdBy   String
+  isPublished Boolean    @default(false)
+  createdAt   DateTime   @default(now())
+  updatedAt   DateTime   @updatedAt
+
+  entries SevaEntry[]
+
+  @@index([tenantId, status])
+  @@index([tenantId, isPublished])
+}
+
+model SevaEntry {
+  id            String          @id @default(cuid())
+  opportunityId String
+  opportunity   SevaOpportunity @relation(fields: [opportunityId], references: [id], onDelete: Cascade)
+  userId        String
+  user          TowerUser       @relation(fields: [userId], references: [id])
+  status        SevaEntryStatus @default(SIGNED_UP)
+  hours         Float?
+  note          String?
+  completedAt   DateTime?
+  createdAt     DateTime        @default(now())
+  updatedAt     DateTime        @updatedAt
+
+  @@unique([opportunityId, userId])
+  @@index([userId])
+}
+
+// Multi-signal gamification — points come from many event types, not just seva.
+enum GamificationEventType {
+  HELPFUL_ANSWER
+  SEVA_COMPLETED
+  EVENT_ATTENDANCE
+  FAQ_APPROVED
+  WELCOME
+  PROFILE_COMPLETED
+  BUSINESS_ADDED
+}
+
+model GamificationEvent {
+  id        String                @id @default(cuid())
+  tenantId  String
+  tenant    Tenant                @relation(fields: [tenantId], references: [id])
+  userId    String
+  user      TowerUser             @relation(fields: [userId], references: [id])
+  type      GamificationEventType
+  points    Int
+  refType   String?
+  refId     String?
+  createdAt DateTime              @default(now())
+
+  @@index([tenantId, userId])
+  @@index([userId, createdAt])
+  // One award per (user, type, ref) — prevents double-awarding the same source.
+  @@unique([userId, type, refId])
+}