Phase 0: stop-the-bleeding bugfixes

- Defer polling_service.start() and FilterEngine init to a one-shot
  before_request hook so importing app.py no longer spawns a scheduler
  thread (also fixes migrate_*.py import side effects).
- Fix migrate_bookmarks.py: init_db returns None, so use the shared
  `db` instead of assigning its None return.
- Enforce MIN_PASSWORD_LENGTH (8) in the password-reset route for
  consistency with signup (was hardcoded 6).
- post_detail.html: replace undefined moment(...).fromNow() (always
  "Recently") with a new timeago Jinja filter + data-timestamp attrs
  that also drive the existing JS updater; make nl2br escape-then-Markup
  and drop | safe from comment/post content to close the XSS hole.
- filter_pipeline: when AI is disabled but a filterset requires it,
  pass posts through with status=FAILED + explicit error instead of
  silently degrading to no_filter.

No source-file mojibake found; content-encoding ingest is a Phase 3 concern.

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

migrate_bookmarks.py

@@ -5,7 +5,7 @@ Migration script to create the bookmarks table.
 
 import os
 import sys
-from database import init_db
+from database import init_db, db
 from flask import Flask
 
 # Add the current directory to Python path
@@ -24,12 +24,13 @@ def main():
     app = create_app()
     
     with app.app_context():
-        # Initialize database
-        db = init_db(app)
-        
+        # Initialize database (init_db binds the shared `db` extension; it
+        # returns None, so use the module-level `db` directly).
+        init_db(app)
+
         # Import models to register them
         from models import User, Session, PollSource, PollLog, Bookmark
-        
+
         # Create all tables (will only create missing ones)
         db.create_all()