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- Concurrency control to cancel outdated runs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/dependabot.yml

@@ -0,0 +1,34 @@
+version: 2
+updates:
+  - package-ecosystem: "cargo"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "monday"
+    open-pull-requests-limit: 10
+    reviewers:
+      - "pandaadir05"
+    labels:
+      - "dependencies"
+      - "rust"
+    commit-message:
+      prefix: "chore"
+      include: "scope"
+    groups:
+      dev-dependencies:
+        dependency-type: "development"
+        update-types:
+          - "minor"
+          - "patch"
+
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "monday"
+    open-pull-requests-limit: 5
+    labels:
+      - "dependencies"
+      - "github-actions"
+    commit-message:
+      prefix: "ci"