Import historical ratings from arbitrary URLs as a background job

The Ratings page gains an "Import ratings" form: paste URLs (one per
line), choose a verdict and an optional note. Rows land in the new
rating_imports table and the new import-ratings job (same systemd job
template as the rest of the catalogue) canonicalizes each URL, reuses or
fetches + extracts the article, embeds it with Voyage when enabled, and
appends an explicit rating event with source "import". Per-URL status
shows on the Ratings page; the job page's journal is the live log.

Imported articles have no entry row (best_entry_id NULL, feed "Imported")
and no sources, so they act as rated neighbours without touching the
feed prior. The CLI's rating-event construction moves to rate::record_explicit
and the dashboard job start path is shared as jobs::start_job.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QVPagF6jfDv78CC5Jv2wp4

src/rate.rs

@@ -0,0 +1,39 @@
+//! Shared construction of explicit rating events.
+
+use crate::config::Config;
+use crate::db::{Db, DbError};
+use crate::types::{ArticleId, RatingEvent, Vote};
+
+/// Append an explicit rating event from a named source.
+pub async fn record_explicit(
+    config: &Config,
+    db: &Db,
+    article_id: ArticleId,
+    vote: Option<Vote>,
+    source: &str,
+    user_id: Option<i64>,
+    note: Option<String>,
+) -> Result<i64, DbError> {
+    let (label, value) = match vote {
+        Some(Vote::Loved) => ("loved", Vote::Loved.value(&config.curation.feedback)),
+        Some(Vote::Good) => ("good", Vote::Good.value(&config.curation.feedback)),
+        Some(Vote::NotForMe) => (
+            "not_for_me",
+            Vote::NotForMe.value(&config.curation.feedback),
+        ),
+        None => ("cleared", 0.0),
+    };
+    db.append_rating_event(&RatingEvent {
+        id: 0,
+        user_id,
+        article_id,
+        issue_date: db.latest_issue_date_for_article(article_id).await?,
+        kind: "explicit".into(),
+        source: source.into(),
+        label: label.into(),
+        value,
+        note,
+        event_at: jiff::Timestamp::now(),
+    })
+    .await
+}