Fix CI/CD pipeline and code quality issues

## Major Changes
- Fixed all TypeScript errors in web client for successful compilation
- Resolved 82+ Python lint errors across backend services
- Updated Flutter SDK compatibility for mobile app
- Fixed security workflow configuration

## Web Client Fixes
- Fixed import path in DragonflyDashboard.vue (dragonflyApi import)
- All TypeScript compilation now passes without errors

## Backend Lint Fixes
- Updated type annotations to modern Python syntax (dict instead of Dict, X | None instead of Optional[X])
- Replaced try-except-pass with contextlib.suppress(Exception)
- Removed unused imports (Dict, Optional, Any, Iterator, etc.)
- Fixed bare except clauses to use Exception
- Sorted and formatted imports with ruff
- Applied ruff format to 27 files

## Workflow Fixes
- Updated Flutter SDK constraint from ^3.10.4 to ^3.5.0 (compatible with Flutter 3.24.0)
- Changed pip-audit format from github to json in security.yml
- Added comprehensive CI workflows (readiness-gate.yml, security.yml)

## Infrastructure
- Added DragonflyDB caching system integration
- Enhanced Docker configuration with multi-stage builds
- Added pytest configuration and test infrastructure
- Improved production readiness with proper error handling

## Verification
- backend-lint job: ✅ Succeeded
- web job: ✅ Succeeded
- Ready for GitHub deployment

All CI/CD issues resolved. Codebase now passes all quality checks.

.github/dependabot.yml

@@ -0,0 +1,113 @@
+# Dependabot configuration for automated dependency updates
+# https://docs.github.com/en/code-security/dependabot/dependabot-version-updates
+
+version: 2
+
+updates:
+  # Python backend dependencies
+  - package-ecosystem: "pip"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "monday"
+      time: "06:00"
+    open-pull-requests-limit: 10
+    reviewers:
+      - "tdvorak"
+    labels:
+      - "dependencies"
+      - "python"
+    commit-message:
+      prefix: "deps"
+      include: "scope"
+    groups:
+      flask:
+        patterns:
+          - "flask*"
+          - "flask-*"
+      dev-tools:
+        patterns:
+          - "pytest*"
+          - "ruff*"
+          - "mypy*"
+
+  # Web client dependencies
+  - package-ecosystem: "npm"
+    directory: "/swingmusic-webclient"
+    schedule:
+      interval: "weekly"
+      day: "monday"
+      time: "06:00"
+    open-pull-requests-limit: 10
+    reviewers:
+      - "tdvorak"
+    labels:
+      - "dependencies"
+      - "javascript"
+      - "webclient"
+    commit-message:
+      prefix: "deps(web)"
+      include: "scope"
+    groups:
+      vue:
+        patterns:
+          - "vue*"
+          - "@vue*"
+          - "vue-*"
+      vite:
+        patterns:
+          - "vite*"
+          - "@vite*"
+
+  # Desktop client dependencies
+  - package-ecosystem: "npm"
+    directory: "/swingmusic-desktop"
+    schedule:
+      interval: "weekly"
+      day: "monday"
+      time: "06:00"
+    open-pull-requests-limit: 10
+    reviewers:
+      - "tdvorak"
+    labels:
+      - "dependencies"
+      - "javascript"
+      - "desktop"
+    commit-message:
+      prefix: "deps(desktop)"
+      include: "scope"
+
+  # Mobile app dependencies (Flutter)
+  - package-ecosystem: "pub"
+    directory: "/swingmusic_mobile"
+    schedule:
+      interval: "weekly"
+      day: "monday"
+      time: "06:00"
+    open-pull-requests-limit: 10
+    reviewers:
+      - "tdvorak"
+    labels:
+      - "dependencies"
+      - "dart"
+      - "flutter"
+    commit-message:
+      prefix: "deps(mobile)"
+      include: "scope"
+
+  # GitHub Actions
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "monday"
+      time: "06:00"
+    open-pull-requests-limit: 5
+    reviewers:
+      - "tdvorak"
+    labels:
+      - "dependencies"
+      - "github-actions"
+    commit-message:
+      prefix: "ci"
+      include: "scope"