feat(integration): add open-reuse Integration Definition for Gitea backend

Register the Gitea API adapter boundary for issue-core maintenance tracking.

integration/gitea-backend.integration.yaml

@@ -0,0 +1,82 @@
+schema_version: open-reuse.integration.v0.1
+id: issue-core-gitea
+name: issue-core Gitea Backend
+description: >
+  Pluggable remote backend that maps the issue-core unified task model onto the
+  Gitea issues API for cross-repo task landing and synchronization.
+status: registered
+owner: issue-core
+
+local:
+  repo: issue-core
+  path: integration/gitea-backend.integration.yaml
+  system: issue-core
+
+upstream:
+  name: Gitea
+  project_url: https://github.com/go-gitea/gitea
+  homepage: https://about.gitea.com/
+  version_policy: gitea-api-v1
+  monitor:
+    releases: true
+    tags: true
+    security_advisories: true
+    license_changes: true
+
+reuse:
+  primary_reuse_mode: adapter
+  secondary_reuse_modes:
+    - plugin
+  risk_level: medium
+  rationale: >
+    Gitea REST API is wrapped behind the RemoteBackend interface; local task
+    lifecycle semantics remain stable across backend swaps.
+
+boundary:
+  type: adapter
+  local_adapter: issue_core.backends.gitea.backend.GiteaBackend
+  local_interface: issue_core.core.interfaces.RemoteBackend
+  reused_surface: Gitea /api/v1 issues, labels, milestones, comments
+  contracts:
+    - issue-core.backend.v1
+  fragility_points:
+    - Gitea API field changes
+    - issue state mapping differences
+    - pagination and rate-limit behavior
+    - authentication token scopes
+
+validation:
+  harness: python3 -m pytest tests/test_gitea_backend.py
+  skip_without_runtime: true
+  checks:
+    - API client request shaping
+    - issue state mapping
+    - error handling for rate limits
+  policy: required-before-update
+
+update_policy:
+  default_action: require-maintainer-review
+  auto_eligible: false
+
+risks:
+  sensitivity:
+    - Gitea API breaking changes
+    - authentication model changes
+    - rate-limit policy changes
+    - license changes
+  escalation_triggers:
+    - validation failure
+    - Gitea major release
+    - production sync errors
+
+maintenance:
+  maintainers:
+    - issue-core
+  escalation_conditions:
+    - Gitea API compatibility failure
+    - validation failure
+    - production backend sync regression
+
+audit:
+  registered_at: "2026-06-24"
+  registered_by: open-reuse