feat(integrations): add S3 and SMTP adapters

Port the legacy server/src/lib/s3.js and mailer.js (eden.md §4/§5) into
packages/integrations behind an adapter/port pattern, isolated from
domain logic per Master Prompt §13.

- s3/client.ts: @aws-sdk/client-s3 wrapper (uploadObject, getObjectStream,
  deleteObject, getClient/getBucket for future multipart Backup uploads).
  Lazily-initialized singleton client, forcePathStyle from
  S3_FORCE_PATH_STYLE (default true). Throws a clear "S3 não configurado
  (S3_ENDPOINT ausente)" whenever S3_ENDPOINT is unset — storage failures
  must be loud, never a silent no-op.

- smtp/mailer.ts: nodemailer wrapper (sendMail). Lazily-initialized
  singleton transporter, secure:true auto-detected on port 465, from
  defaults to SMTP_FROM or SMTP_USER. Deliberately fail-soft: if
  SMTP_HOST is unset, or if sending fails, logs and returns normally —
  no business flow ever fails because of email, matching the legacy's
  behavior exactly.

@eden/config's loadEnv()/env-schema is still a placeholder in this
worktree, so both adapters read process.env directly using the exact
var names already reserved in the target schema; @eden/config is added
as a workspace dependency so this can be swapped for a real loadEnv()
call later without touching callers.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

packages/integrations/package.json

@@ -10,7 +10,13 @@
     "typecheck": "tsc -p tsconfig.json --noEmit",
     "lint": "echo 'no linter configured yet'"
   },
+  "dependencies": {
+    "@aws-sdk/client-s3": "^3.1096.0",
+    "@eden/config": "workspace:*",
+    "nodemailer": "^9.1.1"
+  },
   "devDependencies": {
+    "@types/nodemailer": "^8.0.1",
     "typescript": "^5.7.3"
   }
 }