feat(api,web): Backend-only AI provider configuration and usage cost tracking

packages/mukti-api/src/modules/ai/ai.module.ts

@@ -2,33 +2,61 @@ import { Module } from '@nestjs/common';
 import { ConfigModule } from '@nestjs/config';
 import { MongooseModule } from '@nestjs/mongoose';
 
+import {
+  AiModelConfig,
+  AiModelConfigSchema,
+} from '../../schemas/ai-model-config.schema';
+import {
+  AiProviderConfig,
+  AiProviderConfigSchema,
+} from '../../schemas/ai-provider-config.schema';
 import { User, UserSchema } from '../../schemas/user.schema';
+import { AuthModule } from '../auth/auth.module';
 import { AiController } from './ai.controller';
 import { AiPolicyService } from './services/ai-policy.service';
+import { AiConfigService } from './services/ai-config.service';
+import { AiGatewayService } from './services/ai-gateway.service';
 import { AiSecretsService } from './services/ai-secrets.service';
 import { GeminiClientFactory } from './services/gemini-client.factory';
 import { OpenRouterClientFactory } from './services/openrouter-client.factory';
 import { OpenRouterModelsService } from './services/openrouter-models.service';
+import { AnthropicProviderService } from './services/providers/anthropic-provider.service';
+import { GeminiProviderService } from './services/providers/gemini-provider.service';
+import { OpenAiProviderService } from './services/providers/openai-provider.service';
+import { OpenRouterProviderService } from './services/providers/openrouter-provider.service';
 
 @Module({
   controllers: [AiController],
   exports: [
     AiPolicyService,
+    AiConfigService,
+    AiGatewayService,
     AiSecretsService,
     GeminiClientFactory,
     OpenRouterClientFactory,
     OpenRouterModelsService,
   ],
   imports: [
     ConfigModule,
-    MongooseModule.forFeature([{ name: User.name, schema: UserSchema }]),
+    AuthModule,
+    MongooseModule.forFeature([
+      { name: User.name, schema: UserSchema },
+      { name: AiProviderConfig.name, schema: AiProviderConfigSchema },
+      { name: AiModelConfig.name, schema: AiModelConfigSchema },
+    ]),
   ],
   providers: [
     AiPolicyService,
+    AiConfigService,
+    AiGatewayService,
     AiSecretsService,
     GeminiClientFactory,
     OpenRouterClientFactory,
     OpenRouterModelsService,
+    OpenAiProviderService,
+    AnthropicProviderService,
+    GeminiProviderService,
+    OpenRouterProviderService,
   ],
 })
 export class AiModule {}

packages/mukti-api/src/modules/ai/dto/admin-model.dto.ts

@@ -0,0 +1,83 @@
+import { ApiProperty, ApiPropertyOptional } from '@nestjs/swagger';
+import { Type } from 'class-transformer';
+import {
+  IsBoolean,
+  IsIn,
+  IsNotEmpty,
+  IsNumber,
+  IsOptional,
+  IsString,
+  Min,
+  ValidateNested,
+} from 'class-validator';
+
+import { AI_PROVIDER_VALUES } from '../../../schemas/ai-provider-config.schema';
+
+export class AiModelPricingDto {
+  @ApiProperty({
+    description: 'Prompt price in USD per 1M input tokens',
+    example: 0.15,
+  })
+  @IsNumber()
+  @Min(0)
+  promptUsdPer1M: number;
+
+  @ApiProperty({
+    description: 'Completion price in USD per 1M output tokens',
+    example: 0.6,
+  })
+  @IsNumber()
+  @Min(0)
+  completionUsdPer1M: number;
+}
+
+export class UpsertAiModelDto {
+  @ApiProperty({
+    description: 'Client-facing model label',
+    example: 'GPT-4.1 Mini',
+  })
+  @IsNotEmpty()
+  @IsString()
+  label: string;
+
+  @ApiProperty({
+    description: 'Provider for this model',
+    enum: AI_PROVIDER_VALUES,
+    example: 'openai',
+  })
+  @IsIn(AI_PROVIDER_VALUES)
+  provider: string;
+
+  @ApiProperty({
+    description: 'Provider-specific model identifier',
+    example: 'gpt-4.1-mini',
+  })
+  @IsNotEmpty()
+  @IsString()
+  providerModel: string;
+
+  @ApiProperty({
+    description: 'Pricing configuration for deterministic cost tracking',
+    type: AiModelPricingDto,
+  })
+  @Type(() => AiModelPricingDto)
+  @ValidateNested()
+  pricing: AiModelPricingDto;
+
+  @ApiPropertyOptional({
+    description: 'Whether this model is available to users',
+    example: true,
+  })
+  @IsBoolean()
+  @IsOptional()
+  isActive?: boolean;
+}
+
+export class ToggleAiModelDto {
+  @ApiProperty({
+    description: 'Whether this model is active',
+    example: true,
+  })
+  @IsBoolean()
+  isActive: boolean;
+}

packages/mukti-api/src/modules/ai/dto/admin-provider.dto.ts

@@ -0,0 +1,21 @@
+import { ApiProperty } from '@nestjs/swagger';
+import { IsBoolean, IsNotEmpty, IsString } from 'class-validator';
+
+export class SetProviderApiKeyDto {
+  @ApiProperty({
+    description: 'Provider API key to store on the server',
+    example: 'sk-...',
+  })
+  @IsNotEmpty()
+  @IsString()
+  apiKey: string;
+}
+
+export class ToggleProviderDto {
+  @ApiProperty({
+    description: 'Whether this provider is active for model routing',
+    example: true,
+  })
+  @IsBoolean()
+  isActive: boolean;
+}

packages/mukti-api/src/modules/ai/dto/ai-settings.dto.ts

@@ -3,8 +3,8 @@ import { IsOptional, IsString } from 'class-validator';
 
 export class UpdateAiSettingsDto {
   @ApiPropertyOptional({
-    description: 'Globally active OpenRouter model id',
-    example: 'openai/gpt-5-mini',
+    description: 'Globally active AI model id',
+    example: 'default-gpt-5-mini',
   })
   @IsOptional()
   @IsString()