ci: publish images to the Gitea registry, use the gitea context

Release now pushes to git.lucasrguerra.dev.br instead of ghcr.io, tags each
architecture separately (no artifact upload, no gha cache) and joins them with
imagetools. GITHUB_OUTPUT and GITHUB_STEP_SUMMARY stay: they are the runner's
own interface and the GITEA_* equivalents are not set.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

docker-compose.yaml

@@ -60,7 +60,7 @@ services:
   # probe - a health check on a container that is meant to stop would report
   # unhealthy exactly when it has done its job.
   migrate:
-    image: ${IMAGE_NAMESPACE:-ghcr.io/lucasrguerra/lambdamail}/migrations:${IMAGE_TAG:-latest}
+    image: ${IMAGE_NAMESPACE:-git.lucasrguerra.dev.br/lucasrguerra/lambdamail}/migrations:${IMAGE_TAG:-latest}
     # "latest" is a moving tag and Docker considers a tag it already holds
     # locally to be satisfied, so recreating this container silently reused
     # the cached image and the newly published one was never fetched: the
@@ -80,7 +80,7 @@ services:
 
   # ------------------------------------------------------------ RSPAMD
   rspamd:
-    image: ${IMAGE_NAMESPACE:-ghcr.io/lucasrguerra/lambdamail}/rspamd:${IMAGE_TAG:-latest}
+    image: ${IMAGE_NAMESPACE:-git.lucasrguerra.dev.br/lucasrguerra/lambdamail}/rspamd:${IMAGE_TAG:-latest}
     # "latest" is a moving tag and Docker considers a tag it already holds
     # locally to be satisfied, so recreating this container silently reused
     # the cached image and the newly published one was never fetched: the
@@ -140,7 +140,7 @@ services:
 
   # -------------------------------------------------------------- AUTH
   auth:
-    image: ${IMAGE_NAMESPACE:-ghcr.io/lucasrguerra/lambdamail}/auth:${IMAGE_TAG:-latest}
+    image: ${IMAGE_NAMESPACE:-git.lucasrguerra.dev.br/lucasrguerra/lambdamail}/auth:${IMAGE_TAG:-latest}
     # "latest" is a moving tag and Docker considers a tag it already holds
     # locally to be satisfied, so recreating this container silently reused
     # the cached image and the newly published one was never fetched: the
@@ -178,7 +178,7 @@ services:
 
   # ----------------------------------------------------------- STORAGE
   storage:
-    image: ${IMAGE_NAMESPACE:-ghcr.io/lucasrguerra/lambdamail}/storage:${IMAGE_TAG:-latest}
+    image: ${IMAGE_NAMESPACE:-git.lucasrguerra.dev.br/lucasrguerra/lambdamail}/storage:${IMAGE_TAG:-latest}
     # "latest" is a moving tag and Docker considers a tag it already holds
     # locally to be satisfied, so recreating this container silently reused
     # the cached image and the newly published one was never fetched: the
@@ -214,7 +214,7 @@ services:
 
   # --------------------------------------------------------- PROTOCOLS
   protocols:
-    image: ${IMAGE_NAMESPACE:-ghcr.io/lucasrguerra/lambdamail}/protocols:${IMAGE_TAG:-latest}
+    image: ${IMAGE_NAMESPACE:-git.lucasrguerra.dev.br/lucasrguerra/lambdamail}/protocols:${IMAGE_TAG:-latest}
     # "latest" is a moving tag and Docker considers a tag it already holds
     # locally to be satisfied, so recreating this container silently reused
     # the cached image and the newly published one was never fetched: the
@@ -297,7 +297,7 @@ services:
 
   # -------------------------------------------------------------- WEB
   web:
-    image: ${IMAGE_NAMESPACE:-ghcr.io/lucasrguerra/lambdamail}/webmail:${IMAGE_TAG:-latest}
+    image: ${IMAGE_NAMESPACE:-git.lucasrguerra.dev.br/lucasrguerra/lambdamail}/webmail:${IMAGE_TAG:-latest}
     # "latest" is a moving tag and Docker considers a tag it already holds
     # locally to be satisfied, so recreating this container silently reused
     # the cached image and the newly published one was never fetched: the