feat: mdgrep 0.1.0 – boolean full-text search for Markdown

- query language: substrings, phrases, /regex/, AND/OR/NOT (+ UND/ODER/NICHT),
  parentheses; case-insensitive; ReDoS protection via regex timeouts;
  syntax errors with stable code and position
- SearchEngine over in-memory blocks: filters, predicate, grouping, sorting,
  paging, time budget, automatic reload, highlighted snippets
- Markdown loader with split modes file/heading/list/paragraph
- grep-like CLI (mdgrep), JSON output, grep exit codes
- Flask blueprint/app with JSON API and widget assets, dev server
- framework-free JS widget: live search, URL state, filters, paging,
  syntax help, en/de labels, CSS custom properties for theming

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,6 @@
+.venv/
+__pycache__/
+*.egg-info/
+dist/
+build/
+.pytest_cache/