rename: 3x-ui/x-ui -> L-UI/l-ui/lui-agent (paths, services, env, assets)

Display L-UI; panel binary/process l-ui, agent lui-agent.
Dirs /usr/local/l-ui, /etc/l-ui, /var/log/l-ui; DB /etc/l-ui/l-ui.db
(name file drives it via GetName), probe.db beside it, cert
/etc/l-ui/cert, bin /usr/local/l-ui/bin. Services l-ui.service /
lui-agent.service, OpenRC lui-agent, l-ui.sh, cmd/lui-agent.
Env prefix XUI_ -> LUI_ (code reads new prefix only). Release
assets l-ui-linux-* / lui-agent-linux-*; Gitea repo rogue/l-ui is
a placeholder pending user confirmation (see selfupdate.go note).
Go module path github.com/mhsanaei/3x-ui/v3 intentionally kept.
Versions unchanged: panel V2.6.0 / agent A2.5.0.

.github/workflows/docker.yml

@@ -24,7 +24,7 @@ jobs:
         uses: docker/metadata-action@v6
         with:
           images: |
-            hsanaeii/3x-ui
+            hsanaeii/L-UI
             ghcr.io/mhsanaei/3x-ui
           tags: |
             type=ref,event=branch