v0.1.11

feat: export --format markdown + badge command (v0.1.11)

- `aimemo export --format markdown`: Markdown export grouped by date,
  todos bolded, recaps flagged with emoji, tags in italics
- `aimemo badge`: shields.io static badge showing last session date,
  with example sed command for CI/git-hook automation
- README: sync section rewritten with step-by-step team workflow,
  duplicate detection note, and gitignore guidance
- Bump version to 0.1.11

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>