refactor: Factor out Gitea interfacing into clean facade pattern

- Create new gitea/ package with clean API facade
- Establish proper separation of concerns: tddai uses gitea, not vice versa
- Replace duplicate curl+subprocess patterns with unified HTTP client
- Add rich domain models with properties (issue.priority, issue.status)
- Maintain full backwards compatibility in tddai modules
- Reduce code complexity: -373 lines, +151 lines (net -222 lines)
- Improve testability and maintainability through clean interfaces

Architecture:
- gitea.client.GiteaClient - main facade with sub-clients
- gitea.api_client - high-level API with model conversion
- gitea.http_client - low-level HTTP operations
- gitea.models - rich domain objects (Issue, Milestone, Label)
- gitea.config - gitea-specific configuration
- gitea.exceptions - clean exception hierarchy

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

gitea/__init__.py

@@ -0,0 +1,33 @@
+"""
+Gitea API facade - Clean interface for Gitea repository operations.
+
+This package provides a clean, well-structured interface to Gitea API operations,
+following the facade pattern to decouple application logic from specific API
+implementation details.
+
+Structure:
+- client: Main GiteaClient facade
+- models: Domain models (Issue, Milestone, Label, etc.)
+- config: Gitea-specific configuration
+- exceptions: Gitea-specific exceptions
+
+Usage:
+    from gitea import GiteaClient
+
+    client = GiteaClient()
+    issues = client.issues.list()
+    issue = client.issues.get(42)
+    client.issues.create("Bug fix", "Description")
+"""
+
+from .client import GiteaClient
+from .models import Issue, Milestone, Label, ProjectState, Priority
+from .config import GiteaConfig
+from .exceptions import GiteaError, GiteaAuthError, GiteaNotFoundError
+
+__all__ = [
+    'GiteaClient',
+    'Issue', 'Milestone', 'Label', 'ProjectState', 'Priority',
+    'GiteaConfig',
+    'GiteaError', 'GiteaAuthError', 'GiteaNotFoundError'
+]