Implement comprehensive CI/CD pipeline with best practices

Major improvements:
- Matrix testing across Linux (stable/beta/nightly), Windows, and macOS
- Test with multiple feature combinations (default, yara-scanning, no-default)
- Code coverage reporting with codecov integration
- Security auditing with cargo-audit and dependency review
- Automated release builds for multiple targets
- Performance benchmarking with trend tracking
- Concurrency control to cancel outdated runs
- Rust cache optimization for faster builds
- Documentation generation checks
- Weekly scheduled runs for proactive monitoring

Additional workflows:
- Automated dependency updates via Dependabot
- Weekly Cargo dependency update PRs
- Stale issue and PR management

Project templates:
- Pull request template with checklist
- Bug report issue template
- Feature request issue template
- Codecov configuration with 70% coverage target

.github/workflows/stale.yml

@@ -0,0 +1,36 @@
+name: Issue and PR Cleanup
+
+on:
+  schedule:
+    - cron: '0 0 * * *'
+  workflow_dispatch:
+
+permissions:
+  issues: write
+  pull-requests: write
+
+jobs:
+  stale:
+    name: Mark Stale Issues and PRs
+    runs-on: ubuntu-latest
+    steps:
+      - name: Mark stale issues and PRs
+        uses: actions/stale@v9
+        with:
+          repo-token: ${{ secrets.GITHUB_TOKEN }}
+          stale-issue-message: |
+            This issue has been automatically marked as stale because it has not had recent activity.
+            It will be closed in 7 days if no further activity occurs.
+            If this is still relevant, please add a comment to keep it open.
+          stale-pr-message: |
+            This pull request has been automatically marked as stale because it has not had recent activity.
+            It will be closed in 7 days if no further activity occurs.
+            If you're still working on this, please add a comment or update the PR.
+          close-issue-message: 'This issue was closed because it has been stale for 7 days with no activity.'
+          close-pr-message: 'This PR was closed because it has been stale for 7 days with no activity.'
+          days-before-stale: 30
+          days-before-close: 7
+          stale-issue-label: 'stale'
+          stale-pr-label: 'stale'
+          exempt-issue-labels: 'pinned,security,enhancement'
+          exempt-pr-labels: 'pinned,security'