feat: consolidate scraper into monorepo, remove migration scripts

- Remove one-time migrate.py and tag_subjects.py (already used)
- Add scraper.py: scrapes AoPS wiki and ingests directly into D1
  - Supports --subjects-dir for subject tagging
  - Supports --year for incremental updates
  - Supports --local-backup for file output
- Add pyproject.toml for scraper Python dependencies
- No longer depends on amcProblems, amcSubjects, or amcWorker repos

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: andrewboldi

worker/migrate.py

@@ -0,0 +1,8 @@
+[project]
+name = "amc-scraper"
+version = "2.0.0"
+requires-python = ">=3.10"
+dependencies = [
+    "aiohttp",
+    "tqdm",
+]