feat: format backend logs in json. Issue #98

AGENTS.md

@@ -15,6 +15,7 @@
 - Global API error shape comes from `server/src/main/java/br/com/tasknoteapp/server/controller/RestExceptionController.java`; frontend expects `message` or `fields[].fieldMessage` (`client/src/api-service/api.ts`).
 - Email and password-reset flows are Resend-backed (`server/src/main/java/br/com/tasknoteapp/server/service/ResendEmailService.java`) and render HTML bodies from templates under `server/src/main/resources/email-templates/` via `server/src/main/java/br/com/tasknoteapp/server/templates/EmailTemplate.java`.
 - Backend targets **Java 25** and **Spring Boot 4.x** (`server/pom.xml`).
+- Backend log format is env-driven: plain console by default, ECS JSON when `LOGGING_STRUCTURED_FORMAT_CONSOLE=ecs` (set in `terraform/main.tf` and `compose.prod-like.yaml`; leave unset locally). Log level stays controlled by `ROOT_LOG_LEVEL`.
 
 ## Developer workflows (use these first)
 - Frontend quality gate: `bash tools/check-frontend.sh` (runs `npm ci`, `lint:fix`, `build`, `test:no-watch`).

compose.prod-like.yaml

@@ -25,6 +25,7 @@ services:
       TARGET_ENV: production
       SECURITY_KEY: this-is-a-very-long-security-key-for-dev
       RESEND_APIKEY: invalid-api-key-only-placeholder
+      LOGGING_STRUCTURED_FORMAT_CONSOLE: ecs
     ports: ["8585:8585"]
     image: ghcr.io/thermcampos/tasknote/server:latest
     healthcheck:

server/src/main/resources/application.yml

@@ -11,6 +11,9 @@ logging:
   level:
     root: ${ROOT_LOG_LEVEL:INFO}
     br.com.tasknoteapp: INFO
+  structured:
+    format:
+      console: ${LOGGING_STRUCTURED_FORMAT_CONSOLE:}
 
 resend:
   api-key: ${RESEND_APIKEY:abc123456}

terraform/main.tf

@@ -255,6 +255,10 @@ resource "kubernetes_deployment_v1" "tasknote_backend" {
             name  = "ROOT_LOG_LEVEL"
             value = var.root_log_level
           }
+          env {
+            name  = "LOGGING_STRUCTURED_FORMAT_CONSOLE"
+            value = "ecs"
+          }
           env {
             name = "SECURITY_KEY"
             value_from {