feat: migration DB — table series avec UUID PK (fusionne series_metadata)

Migration 0070:
- Crée table series (id UUID PK, library_id FK, name, description, authors,
  publishers, status, locked_fields, original_name, etc.)
- Peuple depuis books + series_metadata existants
- Ajoute series_id FK à: books, external_metadata_links, anilist_series_links,
  available_downloads, download_detection_results
- Backfill tous les series_id par matching nom

Migration 0071:
- Supprime les colonnes TEXT legacy (books.series, *.series_name)
- Drop table series_metadata (fusionnée dans series)
- Recrée les contraintes UNIQUE sur series_id au lieu de series_name
- Nettoie les rows orphelines (series_id NULL)
- Ajoute index sur series_id dans toutes les tables

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

infra/migrations/0071_drop_series_legacy_columns.sql

@@ -0,0 +1,84 @@
+-- =============================================================================
+-- Migration 0071: Drop legacy TEXT columns now replaced by series_id FK
+-- Prerequisite: migration 0070 must have run and all code must use series_id
+-- =============================================================================
+
+-- 1. Drop old TEXT series column from books (replaced by series_id FK)
+ALTER TABLE books DROP COLUMN IF EXISTS series;
+
+-- 2. Drop old TEXT series_name columns from related tables
+ALTER TABLE external_metadata_links DROP COLUMN IF EXISTS series_name;
+ALTER TABLE anilist_series_links DROP COLUMN IF EXISTS series_name;
+ALTER TABLE available_downloads DROP COLUMN IF EXISTS series_name;
+ALTER TABLE download_detection_results DROP COLUMN IF EXISTS series_name;
+
+-- 3. Drop the old series_metadata table (fused into series)
+DROP TABLE IF EXISTS series_metadata;
+
+-- 4. Drop old composite indexes that relied on series_name text matching
+DROP INDEX IF EXISTS idx_eml_library_series;
+
+-- 5. Add missing indexes on series_id columns
+CREATE INDEX IF NOT EXISTS idx_eml_series_id ON external_metadata_links(series_id);
+CREATE INDEX IF NOT EXISTS idx_asl_series_id ON anilist_series_links(series_id);
+CREATE INDEX IF NOT EXISTS idx_ad_series_id ON available_downloads(series_id);
+CREATE INDEX IF NOT EXISTS idx_ddr_series_id ON download_detection_results(series_id);
+
+-- 6. Update unique constraints to use series_id instead of series_name
+-- external_metadata_links: (library_id, series_name, provider) → (series_id, provider)
+ALTER TABLE external_metadata_links DROP CONSTRAINT IF EXISTS external_metadata_links_library_id_series_name_provider_key;
+DO $$ BEGIN
+    IF NOT EXISTS (
+        SELECT 1 FROM pg_constraint WHERE conname = 'external_metadata_links_series_id_provider_key'
+    ) THEN
+        ALTER TABLE external_metadata_links
+            ADD CONSTRAINT external_metadata_links_series_id_provider_key UNIQUE (series_id, provider);
+    END IF;
+END $$;
+
+-- anilist_series_links: old PK was (library_id, series_name, provider)
+-- Need to recreate with series_id. First drop old PK, add id column, create new PK.
+DO $$ BEGIN
+    -- Add id column if not exists
+    IF NOT EXISTS (
+        SELECT 1 FROM information_schema.columns
+        WHERE table_name = 'anilist_series_links' AND column_name = 'id'
+    ) THEN
+        ALTER TABLE anilist_series_links ADD COLUMN id UUID DEFAULT gen_random_uuid();
+        -- Drop old composite PK
+        ALTER TABLE anilist_series_links DROP CONSTRAINT IF EXISTS anilist_series_links_pkey;
+        -- Set new PK
+        ALTER TABLE anilist_series_links ADD PRIMARY KEY (id);
+        -- Add unique on (series_id, provider)
+        ALTER TABLE anilist_series_links
+            ADD CONSTRAINT anilist_series_links_series_id_provider_key UNIQUE (series_id, provider);
+    END IF;
+END $$;
+
+-- available_downloads: old unique was (library_id, series_name)
+ALTER TABLE available_downloads DROP CONSTRAINT IF EXISTS available_downloads_library_id_series_name_key;
+DO $$ BEGIN
+    IF NOT EXISTS (
+        SELECT 1 FROM pg_constraint WHERE conname = 'available_downloads_series_id_key'
+    ) THEN
+        ALTER TABLE available_downloads
+            ADD CONSTRAINT available_downloads_series_id_key UNIQUE (series_id);
+    END IF;
+END $$;
+
+-- 7. Clean up orphaned rows (series_id IS NULL after migration 0070)
+DELETE FROM external_metadata_links WHERE series_id IS NULL;
+DELETE FROM anilist_series_links WHERE series_id IS NULL;
+DELETE FROM available_downloads WHERE series_id IS NULL;
+DELETE FROM download_detection_results WHERE series_id IS NULL;
+
+-- 8. Make series_id NOT NULL now that all data is migrated
+ALTER TABLE external_metadata_links ALTER COLUMN series_id SET NOT NULL;
+ALTER TABLE anilist_series_links ALTER COLUMN series_id SET NOT NULL;
+ALTER TABLE available_downloads ALTER COLUMN series_id SET NOT NULL;
+-- download_detection_results keeps series_id nullable (temp job data)
+
+-- 9. Drop library_id from tables where it's now redundant (available via series.library_id JOIN)
+-- Keep library_id for now on anilist_series_links and external_metadata_links for query convenience
+-- Only drop from available_downloads and download_detection_results where it's truly redundant
+-- Actually, keep all library_id columns for query performance (avoids extra JOIN)