refactor: rename the gitea-mirror service directory to gitea

docs/gitea/troubleshooting.md

@@ -0,0 +1,18 @@
+# gitea-mirror troubleshooting
+
+Applies to `gitea/compose.yml`.
+
+## Gitea cannot connect after changing `POSTGRES_PASSWORD`
+
+Postgres sets the password only when it first initialises `db-data`. Changing
+`POSTGRES_PASSWORD` later breaks Gitea's connection until the role is altered
+to match:
+
+```sh
+docker compose exec db psql -U gitea -c "ALTER USER gitea PASSWORD '<new>';"
+```
+
+## A redeploy kills clones in progress
+
+Gitea restarts and the clone dies with it. Avoid pushing to `gitea/`
+while a large first mirror runs.