fix: resolve CI failures for lint, test mocking, and Docker build

[GerdsenAI-Admin]

Summary

Fixes all three CI job failures: lint violations, test mock path errors, and Docker build issues.

Changes

Lint Fixes

• Fixed line length violations (>88 chars) in da3_inference_optimized.py and depth_anything_3_node_optimized.py
• Applied Black formatting to all Python files
• Removed unused imports in test/test_inference.py

Test Fixes

• Corrected mock paths from depth_anything_3_ros2.da3_inference.DepthAnything3 to depth_anything_3.api.DepthAnything3 (where the import actually occurs)
• Added actual test logic to test_inference_invalid_input_type to use the imported class

Docker Fixes

• Quoted pip package specifiers in Dockerfile to prevent shell from interpreting <2.0 as a file redirect
• Changed pip install numpy>=1.24.0,<2.0 to pip install "numpy>=1.24.0,<2.0"

Developer Experience

• Added .flake8 config for consistent 88-char line length locally
• Added mypy.ini to suppress missing import errors for optional dependencies
• Updated .vscode/settings.json with project-specific linting settings
• Disabled cSpell and Mypy in VS Code workspace settings

Testing

All CI checks pass locally:

flake8 depth_anything_3_ros2/ --count --select=E9,F63,F7,F82  # 0 errors
flake8 depth_anything_3_ros2/ --count --max-line-length=88   # 0 errors
black --check depth_anything_3_ros2/                          # 7 files unchanged