Record site-name provenance instead of inferring it from the name's shape

Recipe extraction no longer falls back to the URL's host: a stored
recipes.site_name is now always a name the page gave (publisher or
og:site_name), and null when it named none. dinners.SourceOf is the one
documented rule for every fetched recipe's source: the page's name is
shown as it stands; otherwise the site is named by the link's host only
when the link itself is shown as free of secrets, else null. The recipe
detail, idea results and the recipe-candidate offer endpoint all apply
it; candidates no longer carry an extraction-time hostname fallback, so
their site_name is nullable (frontend updated to match).

Migration 0020 clears host-shaped site names (dotted host names, IP
addresses) stored before the change, in recipes and in legacy idea job
results, so already-stored rows read under the same rule.

Maestro 966066e3-0e25-4b8b-9bb0-0694c47c9106

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/settings/RegularsSettingsPage.tsx

@@ -527,13 +527,13 @@ function PickCandidate({ id, onPick }: { id: string; onPick: (candidateId: strin
           <button
             type="button"
             className={styles.candidate}
-            aria-label={`Use ${candidate.title} from ${candidate.site_name}`}
+            aria-label={candidate.site_name === null ? `Use ${candidate.title}` : `Use ${candidate.title} from ${candidate.site_name}`}
             onClick={() => onPick(candidate.candidate_id)}
           >
             <Photo id={candidate.photo_id} name={candidate.title} radius="14px" sizes="56px" className={styles.candidatePhoto} />
             <span className={styles.candidateBody}>
               <span className={styles.candidateTitle}>{candidate.title}</span>
-              <span className={styles.candidateSite}>{candidate.site_name}</span>
+              {candidate.site_name !== null && <span className={styles.candidateSite}>{candidate.site_name}</span>}
             </span>
           </button>
         </li>