feat: add EPUB format support with spine-aware image extraction

Parse EPUB structure (container.xml → OPF → spine → XHTML) to extract
images in reading order. Zero new dependencies — reuses zip + regex
crates with pre-compiled regexes and per-file index cache for
performance. Falls back to CBZ-style image listing when spine contains
no images. Includes DB migration, API/indexer/backoffice updates.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/api/src/books.rs

@@ -102,7 +102,7 @@ pub struct BookDetails {
     tag = "books",
     params(
         ("library_id" = Option<String>, Query, description = "Filter by library ID"),
-        ("kind" = Option<String>, Query, description = "Filter by book kind (cbz, cbr, pdf)"),
+        ("kind" = Option<String>, Query, description = "Filter by book kind (cbz, cbr, pdf, epub)"),
         ("series" = Option<String>, Query, description = "Filter by series name (use 'unclassified' for books without series)"),
         ("reading_status" = Option<String>, Query, description = "Filter by reading status, comma-separated (e.g. 'unread,reading')"),
         ("page" = Option<i64>, Query, description = "Page number (1-indexed, default 1)"),

apps/api/src/pages.rs

@@ -351,6 +351,7 @@ async fn prefetch_page(state: AppState, params: &PrefetchParams<'_>) {
         Some(ref e) if e == "cbz" => "cbz",
         Some(ref e) if e == "cbr" => "cbr",
         Some(ref e) if e == "pdf" => "pdf",
+        Some(ref e) if e == "epub" => "epub",
         _ => return,
     }
     .to_string();
@@ -479,6 +480,7 @@ fn render_page(
         "cbz" => parsers::BookFormat::Cbz,
         "cbr" => parsers::BookFormat::Cbr,
         "pdf" => parsers::BookFormat::Pdf,
+        "epub" => parsers::BookFormat::Epub,
         _ => return Err(ApiError::bad_request("unsupported source format")),
     };
 

apps/api/src/search.rs

@@ -47,7 +47,7 @@ pub struct SearchResponse {
     params(
         ("q" = String, Query, description = "Search query (books + series via PostgreSQL full-text)"),
         ("library_id" = Option<String>, Query, description = "Filter by library ID"),
-        ("type" = Option<String>, Query, description = "Filter by type (cbz, cbr, pdf)"),
+        ("type" = Option<String>, Query, description = "Filter by type (cbz, cbr, pdf, epub)"),
         ("kind" = Option<String>, Query, description = "Filter by kind (alias for type)"),
         ("limit" = Option<usize>, Query, description = "Max results per type (max 100)"),
     ),