docs: add community governance and contribution guidelines

- Add CONTRIBUTING.md with TDD requirements, PR workflow, and AI usage
  policy
- Add CODE_OF_CONDUCT.md based on Contributor Covenant
- Add SECURITY.md with vulnerability reporting scope and process
- Add AGENTS.md with AI usage policy for human contributors and AI
  agents
- Add CLAUDE.md to require reading AGENTS.md before any work
- Add Gitea issue templates for bug reports and feature requests
- Add pull request template with TDD and code quality checklist

.gitea/ISSUE_TEMPLATE/BUG-REPORT.yml

@@ -0,0 +1,97 @@
+name: Bug Report
+description: File a bug report
+title: "[Bug]: "
+labels: ["bug/unconfirmed"]
+body:
+  - type: markdown
+    attributes:
+      value: |
+        Thanks for taking the time to fill out this bug report!
+  - type: textarea
+    id: expected-behaviour
+    attributes:
+      label: Expected behaviour
+      description: How do you expect STA to behave?
+      placeholder: "Relay 3 should turn on after calling POST /api/relays/3/toggle"
+    validations:
+      required: true
+  - type: textarea
+    id: what-happened
+    attributes:
+      label: Actual behaviour
+      description: How does the actual behaviour differ from the expected behaviour?
+      placeholder: "The relay state remains unchanged and the API returns a 500 error"
+    validations:
+      required: true
+  - type: textarea
+    id: reproduction-steps
+    attributes:
+      label: Steps to reproduce
+      description: Step-by-step instructions to reproduce the issue reliably
+      placeholder: |
+        1. Start the STA backend with the following configuration: ...
+        2. Send a POST request to /api/relays/3/toggle
+        3. Observe that ...
+    validations:
+      required: true
+  - type: dropdown
+    id: component
+    attributes:
+      label: Affected component
+      description: Which part of STA is affected?
+      options:
+        - Backend API
+        - Frontend
+        - Modbus hardware communication
+        - Configuration
+        - Other / unsure
+    validations:
+      required: true
+  - type: dropdown
+    id: package-version
+    attributes:
+      label: STA version
+      description: What version of STA are you using?
+      options:
+        - main
+        - develop
+        - something else (please specify)
+  - type: dropdown
+    id: source
+    attributes:
+      label: Source of backend
+      description: From which source did you get the backend?
+      options:
+        - Compiled yourself (Nix development shell)
+        - Compiled yourself (non-Nix development shell)
+        - Release binary
+        - Docker image
+        - something else (please specify)
+  - type: dropdown
+    id: os-platform
+    attributes:
+      label: Operating system and platform
+      description: On which OS and hardware are you running the STA backend?
+      options:
+        - Linux (ARM / Raspberry Pi)
+        - Linux (x86_64)
+        - Other (please specify)
+    validations:
+      required: true
+  - type: textarea
+    id: rust-version
+    attributes:
+      label: Rust version
+      description: If you compiled the binary yourself, which version of Rust did you use?
+      placeholder: "Rust 1.y.z"
+  - type: textarea
+    id: logs
+    attributes:
+      label: Relevant code or log output
+      description: Please copy and paste any relevant code or log output. This will be automatically formatted into code, so no need for backticks.
+      render: text
+  - type: textarea
+    id: other-info
+    attributes:
+      label: Other relevant information
+      description: Please provide any other information which could be relevant to the issue (SQLite version? Upstream bug?)