feat: add blog draft generator and fix broken routes

Blog drafting section (dev-only):
- BlogDraftGenerator gathers project data (gaps, proposals, stats) as
  context and calls Claude to produce Medium-style blog posts
- DB schema: blog_drafts table with title, content, tags, cost tracking
- Web UI: list, generate (async with live preview), detail (rendered +
  source toggle), edit, and export routes
- 6 writing styles: deep-dive, overview, opinion, listicle, comparison,
  series-post
- Nav link added to sidebar under Proposals

Bug fixes found via route testing (scripts/test_all_routes.py):
- /authors/<id>: Draft.status → Draft.states (correct attribute name)
- /false-positives: add missing `import re` in ratings.py

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

src/webui/data/__init__.py

@@ -98,3 +98,9 @@ from webui.data.proposals import (  # noqa: F401
     get_proposal_detail,
     get_proposals_for_gap,
 )
+
+# Blog Drafts
+from webui.data.blog import (  # noqa: F401
+    get_all_blog_drafts,
+    get_blog_draft_detail,
+)