chore: add open-source governance files (GPLv3 + contributing docs)

Add standard open-source project files:
- LICENSE.md — GNU GPL v3.0 or later (verbatim)
- CONTRIBUTING.md — setup, workflow, and required AI-usage disclosure
- CONTRIBUTORS.md — maintainers, contributors, AI-assistance policy
- CODE_OF_CONDUCT.md — Contributor Covenant 2.1
- SECURITY.md — private vulnerability reporting
- .gitea/ISSUE_TEMPLATE/* + PULL_REQUEST_TEMPLATE.md
- README: License section (Copyright (C) 2026 Runic Gateway)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XmHdsbnLzDMAVQkAoTQSBe

.gitea/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,41 @@
+---
+name: Bug report
+about: Report something that is broken or behaving unexpectedly
+title: "[bug] "
+labels:
+  - bug
+---
+
+## Summary
+
+<!-- A clear, concise description of the bug. -->
+
+## Steps to reproduce
+
+1.
+2.
+3.
+
+## Expected behavior
+
+<!-- What you expected to happen. -->
+
+## Actual behavior
+
+<!-- What actually happened. Include exact error messages and logs if you have them. -->
+
+## Environment
+
+- Component / repo:
+- Version or commit:
+- OS / runtime (Node, Rust, ServUO, browser…):
+- Deployment (Docker Compose, local dev, bare metal…):
+
+## Additional context
+
+<!-- Screenshots, config (with secrets redacted), anything else that helps. -->
+
+<!--
+  Security issue? Do NOT file it here. See SECURITY.md and email
+  whitlocktech@gmail.com instead.
+-->

.gitea/ISSUE_TEMPLATE/config.yaml

@@ -0,0 +1,5 @@
+blank_issues_enabled: true
+contact_links:
+  - name: Security vulnerability
+    url: https://gitea.whitlocktech.com/RunicGateway/servuo-plugins/src/branch/main/SECURITY.md
+    about: Please do not open a public issue for security problems — report them privately by email instead (see SECURITY.md).

.gitea/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,23 @@
+---
+name: Feature request
+about: Suggest an idea, enhancement, or new capability
+title: "[feature] "
+labels:
+  - enhancement
+---
+
+## Problem / motivation
+
+<!-- What are you trying to do? What's missing or painful today? -->
+
+## Proposed solution
+
+<!-- What you'd like to see happen. -->
+
+## Alternatives considered
+
+<!-- Other approaches you thought about, and why you prefer the one above. -->
+
+## Additional context
+
+<!-- Mockups, links, related issues, affected component/repo, etc. -->

.gitea/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,33 @@
+<!--
+  Thanks for contributing to Runic Gateway!
+  Please fill out the sections below and check every box before requesting review.
+-->
+
+## What & why
+
+<!-- What does this PR change, and why? Link any related issue: "Closes #123". -->
+
+## How it was tested
+
+<!-- Commands you ran, manual steps, screenshots. -->
+
+## Checklist
+
+- [ ] I have read [CONTRIBUTING.md](CONTRIBUTING.md).
+- [ ] The change builds and existing tests/checks pass locally.
+- [ ] I have added or updated tests/docs where it makes sense.
+- [ ] My commits are reasonably scoped with clear messages.
+
+## AI-assisted contributions (required)
+
+This project **requires disclosure of AI tool usage**. Please pick one:
+
+- [ ] No AI tools were used to produce this contribution.
+- [ ] AI tools were used. Tool(s): `___________`. I have reviewed and understand
+      every change, and take responsibility for it. AI-authored commits are
+      marked with a `Co-Authored-By` / `Assisted-By` trailer.
+
+## License
+
+- [ ] I agree that my contribution is licensed under this project's license
+      (**GNU GPL v3.0 or later**), and I have the right to contribute it.