docs: add JSDoc to service public methods

One-line JSDoc on 82 methods across 11 service files for quick
scanning without reading full implementations.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

shared/modules/economy/economy.service.ts

@@ -8,6 +8,7 @@ import { UserError } from "@shared/lib/errors";
 import { TimerKey, TimerType, TransactionType } from "@shared/lib/constants";
 
 export const economyService = {
+    /** Transfer currency between two users; validates sufficient balance and creates transaction records for both sides. */
     transfer: async (fromUserId: string, toUserId: string, amount: bigint, tx?: Transaction) => {
         if (amount <= 0n) {
             throw new UserError("Amount must be positive");
@@ -69,6 +70,7 @@ export const economyService = {
         }, tx);
     },
 
+    /** Claim the daily reward, applying streak bonuses and weekly bonuses; enforces a UTC-midnight cooldown. */
     claimDaily: async (userId: string, tx?: Transaction) => {
         return await withTransaction(async (txFn) => {
             const now = new Date();
@@ -164,6 +166,7 @@ export const economyService = {
         }, tx);
     },
 
+    /** Adjust a user's balance by the given amount and log a transaction; throws if deduction exceeds current balance. */
     modifyUserBalance: async (id: string, amount: bigint, type: string, description: string, relatedUserId?: string | null, tx?: Transaction) => {
         return await withTransaction(async (txFn) => {
             if (amount < 0n) {