fix: populate canonical_name and stop writing generated normalized_name

Three separate insert paths made a fresh Postgres volume unusable. The live
database only works because its volume predates the constraints.

  - scanner.service.resolveOrCreateArtist inserted only (name), but
    schema.sql declares canonical_name NOT NULL with no default. Every
    artist insert failed, and processFile swallows per-file errors, so a
    scan reported success with 0 tracks and a permanently empty library.
  - enrichment.service inserted explicitly into artists.normalized_name,
    which is GENERATED ALWAYS AS (normalize_artist(name)) STORED:
    "cannot insert a non-DEFAULT value into column" (428C9). All
    enrichment artist creation failed on a fresh volume.
  - db.service.createArtist omitted canonical_name, same failure.

canonical_name holds the raw tag name, not normalize_artist() output,
which truncates on `/` and a standalone `x` ("AC/DC" -> "AC"). That is the
convention createLocalArtist already used. The truncation bug in
artists.name is pre-existing and deliberately left untouched here.

Verified on a scratch postgres:16-alpine with the real schema: the old
statement reproduces the NOT NULL violation, the new path yields
artists/albums/tracks/track_artists rows.

REVIEW-2026-07-30.md finding 1.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

backend/src/services/db.service.ts

@@ -1147,9 +1147,14 @@ export class DbService {
 
   async createArtist(data: Artist): Promise<Artist> {
     const res = await this.pgClient.query(
-      `INSERT INTO artists (name, mbid, discogs_id, image_path)
-       VALUES (normalize_artist($1), $2, $3, $4) RETURNING *`,
-      [data.name, data.mbid, data.discogs_id, data.image_path]
+      // `canonical_name` is NOT NULL with no default, so omitting it fails on a
+      // fresh volume (the live DB's column predates the constraint). It holds the
+      // DISPLAY name: the raw input, not normalize_artist()'s output, which
+      // truncates on `/` and a standalone `x` ("AC/DC" -> "AC"). Matches the
+      // convention in workers' scanner.service.resolveOrCreateArtist.
+      `INSERT INTO artists (name, canonical_name, mbid, discogs_id, image_path)
+       VALUES (normalize_artist($1), $2, $3, $4, $5) RETURNING *`,
+      [data.name, data.name?.trim() || data.name, data.mbid, data.discogs_id, data.image_path]
     );
     return res.rows[0];
   }

workers/src/enrichment.service.ts

@@ -330,14 +330,17 @@ export class EnrichmentService {
           const sortName = mbArtist.sortName || this.generateSortName(canonicalName);
 
           const newArtist = await this.pgClient.query(
-            `INSERT INTO artists (name, canonical_name, sort_name, mbid, normalized_name)
-             VALUES ($1, $2, $3, $4, $5)
+            // normalized_name is a GENERATED ALWAYS column in schema.sql
+            // (normalize_artist(name)); writing to it explicitly errors with
+            // 428C9 on any database built from schema.sql. Let Postgres derive it.
+            `INSERT INTO artists (name, canonical_name, sort_name, mbid)
+             VALUES ($1, $2, $3, $4)
              ON CONFLICT (mbid) DO UPDATE SET
                canonical_name = EXCLUDED.canonical_name,
                sort_name = EXCLUDED.sort_name,
                name = EXCLUDED.name
              RETURNING id`,
-            [rawArtistName, canonicalName, sortName, mbArtist.artistMbid, normalized]
+            [rawArtistName, canonicalName, sortName, mbArtist.artistMbid]
           );
 
           const artistId = newArtist.rows[0].id;
@@ -371,10 +374,12 @@ export class EnrichmentService {
     const sortName = this.generateSortName(rawName);
     
     const result = await this.pgClient.query(
-      `INSERT INTO artists (name, canonical_name, sort_name, normalized_name)
-       VALUES ($1, $2, $3, $4)
+      // normalized_name is GENERATED ALWAYS (normalize_artist(name)) in
+      // schema.sql — inserting it explicitly fails with 428C9. Derived by PG.
+      `INSERT INTO artists (name, canonical_name, sort_name)
+       VALUES ($1, $2, $3)
        RETURNING id`,
-      [rawName, rawName, sortName, normalized]
+      [rawName, rawName, sortName]
     );
     
     const artistId = result.rows[0].id;

workers/src/scanner.service.ts

@@ -237,9 +237,17 @@ export class ScannerService {
       return { id: String(found.rows[0].id), name: String(found.rows[0].name) };
     }
 
+    // `canonical_name` is NOT NULL in schema.sql with no default, so it MUST be
+    // supplied here — omitting it makes every artist insert fail on a fresh
+    // volume (and processFile swallows the error, so the scan silently yields an
+    // empty library). It holds the DISPLAY name: we store the raw tag name, not
+    // the normalize_artist() output, because that function truncates on `/` and
+    // a standalone `x` ("AC/DC" -> "AC", "Felix Mendelssohn" -> "Feli"). The
+    // enrichment path later overwrites canonical_name with the MusicBrainz name;
+    // until then the raw tag is the most faithful display value we have.
     const inserted = await this.pgClient.query(
-      'INSERT INTO artists (name) VALUES ($1) RETURNING id, name',
-      [name]
+      'INSERT INTO artists (name, canonical_name) VALUES ($1, $2) RETURNING id, name',
+      [name, rawName.trim() || name]
     );
     return { id: String(inserted.rows[0].id), name: String(inserted.rows[0].name) };
   }