feat: add gitea-deploy skill, tools, and sdlc foreground service rule

- skills/gitea-deploy/: new skill for Gitea deployment automation
- tools/: shared utility scripts
- skills/sdlc/SKILL.md: add Foreground Service Rule for long-running
  processes (background start + readiness polling pattern)

skills/gitea-deploy/assets/workflow.puml

@@ -0,0 +1,45 @@
+@startuml gitea-deploy-workflow
+skinparam defaultFontName Arial
+skinparam backgroundColor #FAFAFA
+
+actor Developer
+participant "gitea-deploy\nSkill" as SKILL
+participant "Local git" as GIT
+participant "VPS (SSH)" as VPS
+participant "Gitea API" as API
+
+Developer -> SKILL : deploy gitea + push project
+SKILL -> Developer : collect VPS host, SSH user, key, credentials
+
+SKILL -> GIT : git rev-parse (check repo)
+alt not a git repo
+  SKILL -> Developer : offer git init
+  Developer -> GIT : confirm → git init + initial commit
+end
+
+SKILL -> VPS : ssh echo OK (connectivity test)
+alt SSH fails
+  SKILL -> Developer : report error, stop
+end
+
+SKILL -> VPS : docker --version
+alt Docker not installed
+  VPS -> VPS : curl get.docker.com | sh
+end
+
+SKILL -> VPS : upload docker-compose.yml
+SKILL -> VPS : docker compose up -d
+
+loop poll every 5s (max 60s)
+  SKILL -> VPS : curl /api/healthz
+end
+
+SKILL -> VPS : gitea admin user create
+SKILL -> API : POST /api/v1/user/repos
+
+SKILL -> GIT : git remote add gitea ssh://...
+SKILL -> GIT : git push -u gitea --all
+
+SKILL -> API : GET /api/v1/repos/... (verify)
+SKILL -> Developer : report web URL + clone URL
+@enduml