feat: enhance search with FTS5 operators and node scoping

[teal-bauer]

Summary

• Remove forced phrase quoting to enable FTS5 operators (AND, OR, NOT, prefix *, column filters)
• Add in_node scope for searching within a node and its descendants
• Add search form to archive node pages
• Show active node filter on search results with option to remove

Users can now use München OR Munich or Akte NOT geheim instead of only exact phrases. Archive node pages at /archive_nodes/:id have a search field that restricts results to that subtree.

Closes teal-bauer#1
Closes teal-bauer#2

[teal-bauer]

Hye, just wanted to check in if you're still maintaining this, otherwise I'd spin up a fork to extend it