fix: merge duplicate series created by pre-rename scanner bug

Add migration 0063 to fuse series where the scanner recreated an
old filesystem-named entry alongside the user-renamed canonical one
(e.g. "LES MYTHICS" alongside "Mythics"). Uses the original_name
column from 0062 to identify and collapse all such duplicates:
reassigns books, external_metadata_links, anilist_series_links, then
deletes the stale series_metadata row.

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

infra/migrations/0063_merge_duplicate_renamed_series.sql

@@ -0,0 +1,64 @@
+-- Fix duplicate series created when the scanner recreated a filesystem-named
+-- series alongside a user-renamed one.
+-- Example: user renamed "LES MYTHICS" → "Mythics" via UI, but the scanner
+-- also kept (or recreated) a "LES MYTHICS" entry. This migration merges
+-- all such duplicates by using the original_name column added in 0062.
+--
+-- For each canonical series (original_name IS NOT NULL), if a duplicate still
+-- exists with name = original_name in the same library, we:
+--   1. Reassign books from the duplicate to the canonical series
+--   2. Update external_metadata_links
+--   3. Update anilist_series_links
+--   4. Delete the duplicate series_metadata row
+
+-- 1. Reassign books
+UPDATE books b
+SET series = sm_canonical.name
+FROM series_metadata sm_canonical
+JOIN series_metadata sm_dup
+    ON sm_dup.library_id = sm_canonical.library_id
+   AND sm_dup.name = sm_canonical.original_name
+WHERE b.library_id = sm_canonical.library_id
+  AND b.series = sm_dup.name
+  AND sm_canonical.original_name IS NOT NULL;
+
+-- 2. Update external_metadata_links (skip if a row for the canonical name already exists)
+UPDATE external_metadata_links eml
+SET series_name = sm_canonical.name
+FROM series_metadata sm_canonical
+JOIN series_metadata sm_dup
+    ON sm_dup.library_id = sm_canonical.library_id
+   AND sm_dup.name = sm_canonical.original_name
+WHERE eml.library_id = sm_canonical.library_id
+  AND eml.series_name = sm_dup.name
+  AND sm_canonical.original_name IS NOT NULL
+  AND NOT EXISTS (
+      SELECT 1 FROM external_metadata_links eml2
+      WHERE eml2.library_id = eml.library_id
+        AND eml2.series_name = sm_canonical.name
+        AND eml2.provider = eml.provider
+  );
+
+-- 3. Update anilist_series_links (skip if a row for the canonical name already exists)
+UPDATE anilist_series_links asl
+SET series_name = sm_canonical.name
+FROM series_metadata sm_canonical
+JOIN series_metadata sm_dup
+    ON sm_dup.library_id = sm_canonical.library_id
+   AND sm_dup.name = sm_canonical.original_name
+WHERE asl.library_id = sm_canonical.library_id
+  AND asl.series_name = sm_dup.name
+  AND sm_canonical.original_name IS NOT NULL
+  AND NOT EXISTS (
+      SELECT 1 FROM anilist_series_links asl2
+      WHERE asl2.library_id = asl.library_id
+        AND asl2.series_name = sm_canonical.name
+        AND asl2.provider = asl.provider
+  );
+
+-- 4. Delete duplicate series_metadata rows
+DELETE FROM series_metadata sm_dup
+USING series_metadata sm_canonical
+WHERE sm_canonical.library_id = sm_dup.library_id
+  AND sm_canonical.original_name = sm_dup.name
+  AND sm_canonical.original_name IS NOT NULL;