feat(usage): add source/platform tracking + source breakdown in summary

- Add optional 'source' field to UsageDoc (desktop/web/ios/android)
- Add 'source' to UpsertUsageSchema validation
- Include source in upsert document ID to avoid cross-platform overwrites
- Add SourceBreakdown interface
- Aggregate sourceBreakdown in GET /usage/summary alongside modelBreakdown
- Clients can now pass source when reporting usage for per-app analytics

services/platform-service/src/modules/usage/routes.ts

@@ -16,6 +16,7 @@ import {
   CheckLimitsSchema,
   type UsageDoc,
   type ModelBreakdown,
+  type SourceBreakdown,
 } from './types.js';
 
 /**
@@ -63,12 +64,19 @@ export async function usageRoutes(app: FastifyInstance) {
     const records = await repo.list({ userId, days: Number(days), productId });
 
     const byModel: Record<string, { tokens: number; requests: number; cost: number }> = {};
+    const bySource: Record<string, { tokens: number; requests: number; cost: number }> = {};
     for (const r of records) {
       const m = r.model || 'gpt-4o-mini';
       if (!byModel[m]) byModel[m] = { tokens: 0, requests: 0, cost: 0 };
       byModel[m].tokens += r.tokensUsed;
       byModel[m].requests += r.dictations;
       byModel[m].cost += r.costUsd;
+
+      const s = r.source || 'unknown';
+      if (!bySource[s]) bySource[s] = { tokens: 0, requests: 0, cost: 0 };
+      bySource[s].tokens += r.tokensUsed;
+      bySource[s].requests += r.dictations;
+      bySource[s].cost += r.costUsd;
     }
 
     const modelBreakdown: ModelBreakdown[] = Object.entries(byModel).map(([model, s]) => ({
@@ -76,6 +84,11 @@ export async function usageRoutes(app: FastifyInstance) {
       ...s,
     }));
 
+    const sourceBreakdown: SourceBreakdown[] = Object.entries(bySource).map(([source, s]) => ({
+      source,
+      ...s,
+    }));
+
     return {
       totalWords: records.reduce((sum, r) => sum + r.words, 0),
       totalDictations: records.reduce((sum, r) => sum + r.dictations, 0),
@@ -83,6 +96,7 @@ export async function usageRoutes(app: FastifyInstance) {
       totalCost: records.reduce((sum, r) => sum + r.costUsd, 0),
       records,
       modelBreakdown,
+      sourceBreakdown,
     };
   });
 
@@ -95,7 +109,7 @@ export async function usageRoutes(app: FastifyInstance) {
     const input = parsed.data;
     const productId = getRequestProductId(req);
     const doc: UsageDoc = {
-      id: `usg_${input.date}_${input.userId}${input.model ? `_${input.model}` : ''}`,
+      id: `usg_${input.date}_${input.userId}${input.model ? `_${input.model}` : ''}${input.source ? `_${input.source}` : ''}`,
       productId,
       ...input,
       createdAt: new Date().toISOString(),

services/platform-service/src/modules/usage/types.ts

@@ -15,9 +15,17 @@ export interface UsageDoc {
   tokensUsed: number;
   costUsd: number;
   model?: string;
+  source?: string;
   createdAt: string;
 }
 
+export interface SourceBreakdown {
+  source: string;
+  tokens: number;
+  requests: number;
+  cost: number;
+}
+
 export interface UsageSummary {
   totalWords: number;
   totalDictations: number;
@@ -25,6 +33,7 @@ export interface UsageSummary {
   totalCost: number;
   records: UsageDoc[];
   modelBreakdown?: ModelBreakdown[];
+  sourceBreakdown?: SourceBreakdown[];
 }
 
 export interface ModelBreakdown {
@@ -49,6 +58,7 @@ export const UpsertUsageSchema = z.object({
   tokensUsed: z.number().int().min(0).default(0),
   costUsd: z.number().min(0).default(0),
   model: z.string().optional(),
+  source: z.string().optional(),
 });
 
 export const CheckLimitsSchema = z.object({