Fnos packaging (#2524)

* feat(packaging): add fnOS FPK packaging and CI workflow

Add packaging/fnos/ shell (manifest, lifecycle cmd scripts, install/
upgrade/uninstall wizards, desktop entry, EULA) plus in-repo build
script. A release now auto-builds langbot-<tag>-fnos.fpk via
.github/workflows/build-fnos-fpk.yaml, uploaded to the release assets.

* ci(fnos): skip release upload on manual dispatch

github.event.release.tag_name is empty when triggered via
workflow_dispatch, causing 'gh release upload' to fail with
'requires at least 2 arg(s)'. Restrict the step to release events.

* ci(fnos): normalize release asset name

Strip a trailing -fnos from the tag-derived version before appending
the suffix, avoiding langbot-<v>-fnos-fnos.fpk when the tag itself
already carries -fnos.

* ci(fnos): use release tag version for auto build, manifest for manual

Auto build (release/tag) reads version from tag like other release
workflows; build.sh strips the v prefix when injecting into manifest.
Manual dispatch falls back to the version maintained in manifest.

* feat(fnos): add post-install deployment notice to install wizard

Last wizard step now informs users that first startup takes about
5-10 minutes for dependency setup before the web UI is ready.

* docs(fnos): add packaging directory README

* refactor(fnos): rename app from ai.langbot to langbot

Rename appname, desktop entry, data share, build artifacts, and all
references from ai.langbot to langbot across packaging files.

---------

Co-authored-by: dadachann <185672915+dadachann@users.noreply.github.com>

packaging/fnos/manifest

@@ -0,0 +1,16 @@
+appname=langbot
+version=4.10.10
+display_name=LangBot
+desc=基于 LLM 的多平台智能对话机器人，支持 QQ、微信、飞书、钉钉、Telegram 等十余种即时通讯平台，内置 Web 管理界面和 AI Agent 能力。
+platform=all
+source=thirdparty
+maintainer=LangBot
+maintainer_url=https://langbot.app
+service_port=5300
+checkport=true
+os_min_version=0.9.0
+desktop_uidir=ui
+desktop_applaunchname=langbot.main
+ctl_stop=true
+install_dep_apps=nodejs_v22
+changelog=飞牛 fnOS 增强版首版：原生 Python 部署，依赖 Node.js v22 以启用 Box 沙箱 + npx MCP 能力