fix: Update all pipelines to Python 3.14

Python 3.13 is causing installation errors in CI/CD runners.
Upgrading to Python 3.14 which is the latest stable version.

Changes:
- pyproject.toml: Update python requirement to ^3.14
- pyproject.toml: Update MyPy python_version to 3.14
- pyproject.toml: Update Black target-version to py314
- .gitlab-ci.yml: Update PYTHON_VERSION to 3.14
- .github/workflows/build-deploy.yml: Update PYTHON_VERSION to 3.14
- .gitea/workflows/ci.yml: Update PYTHON_VERSION to 3.14

This fixes the CI/CD error:
"rm: cannot remove '/opt/hostedtoolcache/Python/3.13.9/x64/lib/python3.13/__pycache__': Directory not empty"

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

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

pyproject.toml

@@ -8,7 +8,7 @@ readme = "README.md"
 packages = [{include = "datacenter_docs", from = "src"}]
 
 [tool.poetry.dependencies]
-python = "^3.13"
+python = "^3.14"
 
 # Web Framework
 fastapi = "^0.115.0"
@@ -100,7 +100,7 @@ build-backend = "poetry.core.masonry.api"
 
 [tool.black]
 line-length = 100
-target-version = ['py313']
+target-version = ['py314']
 include = '\.pyi?$'
 
 [tool.ruff]
@@ -115,7 +115,7 @@ ignore = ["E501"]
 "src/datacenter_docs/api/main_enhanced.py" = ["F821"]
 
 [tool.mypy]
-python_version = "3.13"
+python_version = "3.14"
 warn_return_any = true
 warn_unused_configs = true
 disallow_untyped_defs = true