Implementa S02: config, main bootstrap y manejo de errores

[YAustinXYZ]

⚠️ REQUIRED — Linked issue

Closes #16

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PR title

feat(config): bootstrap ConfigModule, production main.ts and global exception filter

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Description

Implements S02 — Application core for the Ding Payments server.

Sets up the foundational layer that every future module depends on:
validated environment configuration, a production-ready server bootstrap,
and a uniform error format across all API responses.

Without this deliverable, no other module can be safely built — missing
env vars would cause silent failures and error responses would be inconsistent.

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Type of change

• New feature (feat)
• Bug fix (fix)
• Refactor / internal improvement
• Database migration (Prisma)
• Documentation
• Tests
• Other

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Changes made

• src/config/env.validation.ts — Joi schema that validates all environment
  variables on startup; server refuses to boot if any required variable is missing
• src/config/configuration.ts — Typed configuration object grouped by domain
  (app, database, supabase, stellar, webauthn, payments, throttle)
• src/app.module.ts — Global ConfigModule registration with Joi validation schema
• src/main.ts — Production-ready bootstrap: Helmet, compression, CORS from env,
  global ValidationPipe (whitelist + forbidNonWhitelisted), URI versioning /v1,
  Swagger at /v1/docs, graceful shutdown
• src/common/filters/http-exception.filter.ts — Global exception filter that
  catches NestJS HttpExceptions, Prisma errors (P2002, P2025), and unexpected
  errors; always returns uniform JSON format; never exposes stack traces in production

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Test plan

• npm run start:dev starts without errors
• Removing a required env var from .env causes server to refuse startup with a clear message
• GET /v1/nonexistent returns JSON { statusCode, message, timestamp, path } — not NestJS default HTML
• Swagger UI accessible at http://localhost:3000/v1/docs
• npm run lint passes with zero errors
• Unit / e2e tests updated or added
• Tested locally with npm run start:dev

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Migrations / database

N/A

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Checklist

• I included Closes # with the correct issue number
• Code follows project conventions (NestJS, modules, etc.)
• npm run lint and npm run test pass without errors
• Prisma migrations generated and tested (if applicable)
• Updated documentation if the change requires it

[JoelVR17]

Great job!