SeaORM: feeds and scanning; rusqlite gone

The last nineteen functions move to SeaORM: recording feeds, items and
enclosures, managed OPML feeds, folding WordPress's repeated files, and handing a
Patreon creator's files to its shows. Two SQLite-only forms go: GLOB becomes a
LIKE with the underscore escaped (broader, harmlessly: the fold still keys on
`_=` and digits), and UPDATE OR IGNORE becomes an UPDATE ... WHERE NOT EXISTS.
The two transactions are SeaORM transactions.

With nothing left on it, rusqlite goes, with the SQL schema and migrate(). The
entities are the schema: create_missing makes whatever tables and indexes a
database lacks, from them, with CREATE ... IF NOT EXISTS. Production's schema
already has every column migrate() added and none it dropped.

Not SeaORM's schema sync, used until now: despite its docs it drops a unique
index the entities do not describe, so it dropped users_name_lower on every open.
Every `ipx` command then took a write lock, and against a daemon busy writing,
`ipx status` -- the healthcheck -- failed 7 times in 15 where the old code
failed none. Now 15 in 15, as before. On Postgres it would not have started.

WAL is set only when a file is not already in it: setting it takes a lock that
cannot wait out a busy daemon.

Checked on copies of production: a forced scan of all 162 feeds against the real
feeds with no database errors; the feed list, filters, sorts, search and the
reaper's candidates against the old code on the same data, earlier in the
branch. The column comments from the SQL schema move to the entities.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -9,6 +9,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 
+- The database is reached through SeaORM, on the way to Postgres (issue #18); it is still the
+  same SQLite file, and nothing you see changes. A database from before 0.7 has to be opened by a
+  0.7 release first, which brings its tables up to date.
 - A pinned item sits at the top of its list, above everything else in whatever order you sort
   by, and moves there the moment you pin it. Sorting by the pin column itself still goes both
   ways, and Currently Listening keeps its own order.