chore: improve pre-commit hook — auto-install deps, add Python/Dart lint

Problem

The current pre-commit hook silently skips linting when node_modules are missing (exit 0). This allows badly formatted code to reach CI, causing pipeline failures that could have been caught locally.

Also: Python (ruff) and Dart files are not covered by the pre-commit hook at all.

Changes

# Before: silent skip when no node_modules
if [ "$has_deps" = false ]; then
  echo "⚠ Pre-commit: node_modules not found. Lint will run in CI."
  exit 0  # ← silently passes badly formatted code
fi
npx lint-staged

# After: auto-install only what's needed, lint everything
- npm ci only for components with staged files (not all at once)
- ruff check --fix + ruff format on staged .py files  
- dart format on staged .dart files
- Explicit failure if npm ci fails (with fix instructions)

Behavior Matrix

Language	Tool	Trigger	Auto-install
JS/Vue	eslint + prettier (lint-staged)	Staged .js, .vue	npm ci in affected component only
Python	ruff check + ruff format	Staged .py	N/A (global binary)
Dart	dart format	Staged .dart	N/A (SDK)

Testing

• Hook is executable and has valid shebang
• lint-staged config in package.json unchanged (JS/Vue still works)
• CI pipeline will validate