docs(ospo): add community health files

[DeepDiver1975]

Summary

Incorporates the Kiteworks OSPO community health rollout v2 (adapted from owncloud/web#13815) into this repository.

The source PR targets the owncloud/web frontend (AGPL-3.0, Vue/TypeScript/pnpm monorepo). This repo is the ownCloud Server Docker image build (MIT, Dockerfiles + bash overlays, GitHub Actions), so every repo-specific fact was replaced accordingly.

Changes

• README.md — additive (no existing content removed, since the README is synced to Docker Hub as the image description). Adds an OSPO badge and Community & Support, Contributing, Security, and About the ownCloud OSPO sections.
• agents.md (new) — AI-agent context rewritten for this repo: Dockerfile/overlay layout, GitHub Actions build (main.yml), Trivy/smoke-test flow, and OSPO git/Actions policy.
• CODE_OF_CONDUCT.md / CONTRIBUTING.md / SECURITY.md / SUPPORT.md (new) — community health files; CONTRIBUTING adds repo-specific Docker/PR-workflow notes.
• CHANGELOG.md — dated entry following this repo's flat date-based convention (not a changelog/unreleased/ dir).

Adaptation notes

• License framed as MIT (permissive, already Apache-2.0 compatible) — the AGPL "Category X / copyleft audit / KDE heritage" prerequisites from the source PR are explicitly not carried over.
• No Vue/pnpm/Vitest/Transifex/oCIS-frontend content leaked from the source PR.

Test plan

• README renders on GitHub: existing Docker reference intact + new sections present, links resolve
• Relative links (CONTRIBUTING/CODE_OF_CONDUCT/SECURITY/SUPPORT) resolve to the new files
• agents.md loads correctly in AI agents
• License referenced in README matches the MIT LICENSE file

🤖 Generated with Claude Code

[DeepDiver1975]

Code Review

Overview: Kiteworks OSPO community health file rollout — adds standard GitHub community health files and updates the README with community/OSPO sections.

Files added:

• CODE_OF_CONDUCT.md — links to ownCloud CoC at owncloud.com
• CONTRIBUTING.md — documents rebase workflow, required PGP + DCO signing, Conventional Commits, and GitHub Actions policy
• SECURITY.md — directs vulnerability reports to security.owncloud.com and the YesWeHack bug bounty
• SUPPORT.md — lists enterprise support, community discussions, Matrix chat, and docs channels
• agents.md — AI agent context file documenting repo architecture, build system, conventions, and OSPO policy constraints

README updates: New "Community & Support", "Contributing", "Security", and "About the ownCloud OSPO" sections, plus an OSPO badge.

agents.md content: Well-structured. Accurately describes the repo as a Docker image packaging repo (not the ownCloud source), explains the two v*/ variants, the GitHub Actions build, and the overlay mechanism. The OSPO policy constraints section is directly useful for AI agents working in this repo.

One minor note: CONTRIBUTING.md shows git commit -S -s -m "..." (uppercase -S for GPG, lowercase -s for DCO signoff). The README contributing section shows the same. This is consistent, though the README body also mentions "PGP/GPG signed" while agents.md says PGP/GPG — all consistent.

No concerns. Standard OSPO health file addition.