feat: find a file by any hash, out of the search

Hashes, link lists, install commands, member tables and long reference
tables leave the site search: the index drops from 21.0 MB (4.88 MB
gzip) to 6.8 MB (1.33 MB gzip). Names and prose stay searchable.

files/?hash= takes a SHA1, MD5, CRC32 or SHA256 and reads one shard of
api/v1/lookup/ (about 22 KB gzip, was 675 KB) listing the collection
card, the platforms that declare the value and the profiles that check
it. files/?sha1= still opens the card, and a sha1- anchor missing from
a page is looked up there, so a card can move between pages.

Excluded blocks are section elements: the search plugin compares
elements by tag, so a div ended at the first nested div.

mkdocs.yml

@@ -835,7 +835,7 @@ nav:
   - Dump provenance: provenance.md
   - Updated platform files: exports.md
   - Data and API: data.md
-  - Find a file by its SHA1: files/index.md
+  - Find a file: files/index.md
   - Data model: wiki/data-model.md
   - Architecture: wiki/architecture.md
   - Build your own packs: wiki/advanced-usage.md