Enrich IQDB candidates; link downloads the e621 original

- IQDB responses carry no preview/file data, so candidates only showed an
  ID; the SPA now enriches them with one batched posts lookup (preview,
  rating, score, favourites, dimensions, tag preview)
- Candidate tiles are selectable instead of instantly resolving: picking
  one shows its info and an explicit 'Link selected post' button
- Linking a post now fetches the e621 original into the library and
  drops the staged upload; when the staged file's MD5 already equals the
  post's file, the staged copy is moved instead (identical bytes)
- Keep the file URL in stored e621 metadata; sanitize the new candidate
  fields server-side

frontend/src/lib/e621.ts

@@ -322,6 +322,26 @@ export interface E621IqdbResult {
   preview_url: string | null;
   rating: string | null;
   md5: string | null;
+  score_total: number | null;
+  fav_count: number | null;
+  width: number | null;
+  height: number | null;
+  tags_preview: string[];
+}
+
+function flattenTagPreview(tags: unknown, limit = 8): string[] {
+  if (!tags || typeof tags !== "object") return [];
+  const out: string[] = [];
+  for (const value of Object.values(tags as Record<string, unknown>)) {
+    if (!Array.isArray(value)) continue;
+    for (const tag of value) {
+      if (typeof tag === "string" && !out.includes(tag)) {
+        out.push(tag);
+        if (out.length >= limit) return out;
+      }
+    }
+  }
+  return out;
 }
 
 function normalizeIqdbEntry(entry: unknown): E621IqdbResult | null {
@@ -344,12 +364,18 @@ function normalizeIqdbEntry(entry: unknown): E621IqdbResult | null {
       : typeof post.id === "number"
         ? post.id
         : null;
+  const scoreTotal = post.score;
   return {
     post_id: postId,
     score: typeof record.score === "number" ? record.score : null,
     preview_url: typeof preview.url === "string" ? preview.url : null,
     rating: typeof post.rating === "string" ? post.rating : null,
     md5: typeof file.md5 === "string" ? file.md5 : null,
+    score_total: typeof scoreTotal === "number" ? scoreTotal : null,
+    fav_count: typeof post.fav_count === "number" ? post.fav_count : null,
+    width: typeof file.width === "number" ? file.width : null,
+    height: typeof file.height === "number" ? file.height : null,
+    tags_preview: flattenTagPreview(post.tags),
   };
 }
 
@@ -371,13 +397,44 @@ export async function iqdbSearch(
     : Array.isArray((data as { matches?: unknown[] })?.matches)
       ? (data as { matches: unknown[] }).matches
       : [];
-  return list
+  const candidates = list
     .map(normalizeIqdbEntry)
     .filter(
       (entry): entry is E621IqdbResult =>
         entry !== null && (entry.post_id !== null || entry.preview_url !== null),
     )
     .slice(0, 10);
+
+  // The IQDB payload carries no preview/file data; enrich with one batched
+  // post lookup so candidates can show what they actually are.
+  const ids = candidates
+    .map((candidate) => candidate.post_id)
+    .filter((id): id is number => typeof id === "number");
+  if (ids.length > 0) {
+    try {
+      const posts = await fetchPostsByIds(credentials, ids, signal);
+      const byId = new Map(posts.map((post) => [post.id, post]));
+      return candidates.map((candidate) => {
+        const post =
+          candidate.post_id !== null ? byId.get(candidate.post_id) : undefined;
+        if (!post) return candidate;
+        return {
+          ...candidate,
+          preview_url: post.preview.url ?? candidate.preview_url,
+          rating: post.rating ?? candidate.rating,
+          md5: post.file.md5 ?? candidate.md5,
+          score_total: post.score.total,
+          fav_count: post.fav_count,
+          width: post.file.width,
+          height: post.file.height,
+          tags_preview: flattenTagPreview(post.tags),
+        };
+      });
+    } catch {
+      // Keep the base candidates when the enrichment request fails.
+    }
+  }
+  return candidates;
 }
 
 export function postIsBlacklisted(

frontend/src/lib/types.ts

@@ -113,6 +113,11 @@ export interface E621IqdbCandidate {
   preview_url: string | null;
   rating: string | null;
   md5: string | null;
+  score_total?: number | null;
+  fav_count?: number | null;
+  width?: number | null;
+  height?: number | null;
+  tags_preview?: string[];
 }
 
 export interface TempUpload {