Add CI/CD workflows and security policy

.github/workflows/lint.yml

@@ -0,0 +1,63 @@
+# Check code style and formatting
+name: Lint
+
+on:
+  push:
+    branches: [main, master, develop]
+  pull_request:
+    branches: [main, master, develop]
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    
+    steps:
+      # 1. Get the code
+      - name: Checkout code
+        uses: actions/checkout@v4
+      
+      # 2. Set up Python
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+      
+      # 3. Install linting tools
+      - name: Install linters
+        run: |
+          python -m pip install --upgrade pip
+          pip install ruff black
+      
+      # 4. Run ruff (fast linter - catches bugs and style issues)
+      - name: Run ruff
+        run: |
+          ruff check src/ tests/ frontends/
+      
+      # 5. Check black formatting (doesn't modify, just checks)
+      - name: Check black formatting
+        run: |
+          black --check src/ tests/ frontends/
+
+  # Type checking (optional but helpful)
+  typecheck:
+    runs-on: ubuntu-latest
+    
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+      
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+      
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install -e ".[dev]"
+          pip install mypy
+      
+      - name: Run mypy
+        run: |
+          mypy src/stegasoo --ignore-missing-imports
+        continue-on-error: true  # Don't fail build on type errors (yet)