fix(ci): resolve PEP 668 Python environment issues using venv

Solutions Applied:
✓ core job: Python venv for dependency isolation
  - /usr/bin/python3 -m venv $HOME/venv
  - Prevents 'externally-managed-environment' error
  - pip install within venv (no --break-system-packages)
  - PYTHONPATH points to site-packages

✓ workflow-lint job: Separate venv for yaml parsing
  - /usr/bin/python3 -m venv $HOME/venv_lint
  - PyYAML installed in isolated environment
  - Avoids PEP 668 conflicts

✓ Configure Runtime Paths: Create Temp directory
  - mkdir -p Temp
  - Ensures output files can be written
  - Solves FileNotFoundError for validation reports

Why venv instead of --break-system-packages:
- More portable and maintainable
- Follows Python best practices (PEP 668)
- No system package contamination
- Reproducible across environments

Expected Results:
✓ Setup Python Environment: No more externally-managed error
✓ Python imports: No more ModuleNotFoundError
✓ File writes: No more FileNotFoundError

Phase 0 Week 1: CI Baseline Refinement (Attempt 6)

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -50,6 +50,10 @@ jobs:
       run: |
         export PATH=/usr/local/bin:$PATH
         echo "/usr/local/bin" >> $GITHUB_PATH
+
+        # Ensure Temp directory exists
+        mkdir -p Temp
+
         echo "=== 런타임 확인 ==="
         /usr/bin/python3 --version
         node --version
@@ -57,13 +61,20 @@ jobs:
 
     - name: Setup Python Environment
       run: |
-        PYTHON_DEPS="$HOME/python_deps/core"
-        mkdir -p "$PYTHON_DEPS"
-        /usr/bin/python3 -m pip install --disable-pip-version-check --quiet --upgrade pip setuptools wheel
-        /usr/bin/python3 -m pip install --disable-pip-version-check --quiet \
-          --target "$PYTHON_DEPS" requests pyyaml openpyxl pytest psycopg
-        echo "PYTHONPATH=$PYTHON_DEPS:${PYTHONPATH:-}" >> $GITHUB_ENV
-        /usr/bin/python3 -c 'import sys; sys.path.insert(0, "'$PYTHON_DEPS'"); import requests, yaml, openpyxl, pytest, psycopg; print("✓ Python dependencies installed")'
+        # Create virtual environment (PEP 668 compliant)
+        /usr/bin/python3 -m venv $HOME/venv
+        source $HOME/venv/bin/activate
+
+        # Upgrade pip and install packages
+        pip install --disable-pip-version-check --quiet --upgrade pip setuptools wheel
+        pip install --disable-pip-version-check --quiet requests pyyaml openpyxl pytest psycopg
+
+        # Add venv to PATH and PYTHONPATH
+        echo "$HOME/venv/bin" >> $GITHUB_PATH
+        echo "PYTHONPATH=$HOME/venv/lib/python3.12/site-packages:${PYTHONPATH:-}" >> $GITHUB_ENV
+
+        # Verify installation
+        python3 -c 'import requests, yaml, openpyxl, pytest, psycopg; print("✓ Python dependencies installed")'
 
     - name: Apply Database Migrations
       env:
@@ -443,12 +454,19 @@ jobs:
 
     - name: Setup Python Environment
       run: |
-        PYTHON_DEPS="$HOME/python_deps/lint"
-        mkdir -p "$PYTHON_DEPS"
-        /usr/bin/python3 -m pip install --disable-pip-version-check --quiet \
-          --target "$PYTHON_DEPS" pyyaml
-        echo "PYTHONPATH=$PYTHON_DEPS:${PYTHONPATH:-}" >> $GITHUB_ENV
-        echo "✓ Python dependencies installed"
+        # Create virtual environment (PEP 668 compliant)
+        /usr/bin/python3 -m venv $HOME/venv_lint
+        source $HOME/venv_lint/bin/activate
+
+        # Install YAML parser
+        pip install --disable-pip-version-check --quiet pyyaml
+
+        # Add venv to PATH
+        echo "$HOME/venv_lint/bin" >> $GITHUB_PATH
+        echo "PYTHONPATH=$HOME/venv_lint/lib/python3.12/site-packages:${PYTHONPATH:-}" >> $GITHUB_ENV
+
+        # Verify
+        python3 -c 'import yaml; print("✓ PyYAML installed")'
 
     - name: Lint CI Workflow
       run: python3 tools/validate_gitea_ci_workflow_lint_v1.py --workflow .gitea/workflows/ci.yml