feat(analysis): add ocrs OCR backend and OCR-driven page text search

Adds an in-process ocrs OCR backend as the active analysis engine
(vision left dormant), enables OCR text search on the page-tag
aggregation endpoints, and reshapes the admin analysis/settings UI to
present the OCR-only surface. Bumps version 0.89.0 -> 0.90.0.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/src/api/page_tags.rs

@@ -392,10 +392,9 @@ pub struct AggregateParams {
     pub limit: i64,
     #[serde(default)]
     pub offset: i64,
-    /// Reserved for the planned OCR text-search input. Accepted on
-    /// the wire so adding OCR later won't break the API shape, but
-    /// rejected with 501 `text_search_not_yet_supported` if non-empty
-    /// until the backend supports it.
+    /// OCR text filter. When non-empty, only pages whose analysis
+    /// `search_doc` matches the query (`plainto_tsquery`) are aggregated.
+    /// Blank/absent ⇒ tag-only aggregation.
     #[serde(default)]
     pub text: Option<String>,
 }
@@ -411,32 +410,17 @@ fn parse_order(raw: Option<&str>) -> AppResult<Order> {
     }
 }
 
-fn ensure_text_unsupported(text: Option<&str>) -> AppResult<()> {
-    // Future OCR search will plug in here. Until then, return a
-    // distinct code (`text_search_not_yet_supported`) so clients can
-    // detect "feature pending" vs. a generic 4xx — the code is the
-    // wire contract, not the message.
-    if text.is_some_and(|s| !s.trim().is_empty()) {
-        return Err(AppError::NotImplemented {
-            code: "text_search_not_yet_supported",
-            message: "text search is reserved for the planned OCR input but not yet supported",
-        });
-    }
-    Ok(())
-}
-
 async fn list_chapters_for_tag(
     State(state): State<AppState>,
     CurrentUser(user): CurrentUser,
     Query(params): Query<AggregateParams>,
 ) -> AppResult<Json<PagedResponse<TaggedChapterAggregate>>> {
-    ensure_text_unsupported(params.text.as_deref())?;
     let tag = normalize_tag(&params.tag)?;
     let order = parse_order(params.order.as_deref())?;
     let limit = params.limit.clamp(1, 200);
     let offset = params.offset.max(0);
     let (items, total) = repo::page_tag::aggregate_chapters_for_tag(
-        &state.db, user.id, &tag, order, limit, offset,
+        &state.db, user.id, &tag, order, limit, offset, params.text.as_deref(),
     )
     .await?;
     Ok(Json(PagedResponse::with_total(items, limit, offset, total)))
@@ -447,13 +431,12 @@ async fn list_mangas_for_tag(
     CurrentUser(user): CurrentUser,
     Query(params): Query<AggregateParams>,
 ) -> AppResult<Json<PagedResponse<TaggedMangaAggregate>>> {
-    ensure_text_unsupported(params.text.as_deref())?;
     let tag = normalize_tag(&params.tag)?;
     let order = parse_order(params.order.as_deref())?;
     let limit = params.limit.clamp(1, 200);
     let offset = params.offset.max(0);
     let (items, total) = repo::page_tag::aggregate_mangas_for_tag(
-        &state.db, user.id, &tag, order, limit, offset,
+        &state.db, user.id, &tag, order, limit, offset, params.text.as_deref(),
     )
     .await?;
     Ok(Json(PagedResponse::with_total(items, limit, offset, total)))