srrdb: harvest the srrDB search API into a separate SQLite database

New scope reading the API instead of scraping HTML: one search path per run,
passed raw through --single-uri, and the answer stored as-is into its own
SQLite file created from the embedded schema.

Command line: --single-uri carries the path after /v1/search/
(category:flac/date:today/page:1) and must name a category; --sleep sets the
pause between pages, with the config value as fallback. A day named on the
command line is always fetched again and its dump rewritten, so cron can
refresh today hourly and yesterday daily.

Date placeholders: date:auto walks backwards to the newest day in
[srrdb.floor..yesterday] that has no dump yet, closing holes instead of
declaring the archive covered. date:today, date:yesterday and date:tomorrow
stand for the neighbouring days. Today is never taken by the walk, because a
day still being filled would be frozen by its own dump after the first run.

Dumps are the cursor as well as the record, so a missing dump directory is an
error instead of "nothing harvested yet": a renamed, unmounted or mistyped
directory must not send the run silently back to the beginning. An empty day is
a normal result and is remembered as harvested; API warnings never are, and
they reach the exit code.

Writes go through one transaction, so a day lands completely or not at all.
group and category come from the release line and the search path; status, nfo,
content and synced_at stay NULL. srrdb.log.jsonl records one line per finished
run, srrdb.error_log.jsonl keeps failures and API warnings apart by a kind
field.

Also: the console command contract returns (string, error), so a failing scope
reaches the process exit code and cron can tell a failed run from a successful
one. config/scope/srrdb.yaml is untracked because its paths differ per host.
modernc.org/sqlite replaces the archived libsql client, which only ever talked
to a server. pkg/repository/srrdb.go is split by responsibility and covered by
table-driven tests.

types/model/srrdb.go

@@ -0,0 +1,22 @@
+package model
+
+// SrrdbRelease is one row of the srrdb_releases table described by
+// internal/db/srrdb.sql. Release is the primary key, therefore a repeated
+// search rewrites the previous row of the same release instead of inserting
+// a copy. Columns left nil are stored as NULL.
+type SrrdbRelease struct {
+	Release   string  `db:"release"`
+	Date      string  `db:"date"`
+	HasNfo    string  `db:"has_nfo"`
+	HasSrs    string  `db:"has_srs"`
+	IsForeign string  `db:"is_foreign"`
+	ImdbID    *string `db:"imdb_id"`
+	Size      int64   `db:"size"`
+	GroupName string  `db:"group_name"`
+	Category  string  `db:"category"`
+	Status    *string `db:"status"`
+	Nfo       []byte  `db:"nfo"`
+	Content   *string `db:"content"`
+	CreatedAt string  `db:"created_at"`
+	SyncedAt  *string `db:"synced_at"`
+}