feat(db): add embedded auto-migrating schema system

Replace 4 independent schema management code paths (Docker shell
script, setup wizard pg_restore, test helpers, manual psql) with a
single migration runner embedded in the server binary.

The new server/migrations/ package uses Go embed to bundle all SQL
schemas. On startup, Migrate() creates a schema_version tracking
table, detects existing databases (auto-marks baseline as applied),
and runs pending migrations in transactions.

Key changes:
- Consolidated init.sql + 9.2-update + 33 patches into 0001_init.sql
- Setup wizard simplified to single "Apply schema" checkbox
- Test helpers use migrations.Migrate() instead of pg_restore
- Docker no longer needs schema volume mounts or init script
- Seed data (shops, events, gacha) embedded and applied via API
- Future migrations just add 0002_*.sql files — no manual steps

.github/workflows/go.yml

@@ -81,7 +81,6 @@ jobs:
           ./www/
           ./savedata/
           ./bin/
-          ./bundled-schema/
         retention-days: 7
 
     - name: Build Windows-amd64
@@ -97,7 +96,6 @@ jobs:
           ./www/
           ./savedata/
           ./bin/
-          ./bundled-schema/
         retention-days: 7
 
   lint:

.github/workflows/release.yml

@@ -45,9 +45,7 @@ jobs:
         cp config.example.json staging/
         cp -r www/ staging/www/
         cp -r savedata/ staging/savedata/
-        cp -r schemas/ staging/schemas/
-        # Create a standalone SCHEMA.sql from init schema for convenience
-        cp schemas/init.sql staging/SCHEMA.sql
+        # Schema is now embedded in the binary via server/migrations/
         cd staging && zip -r ../erupe-${{ matrix.os_name }}.zip .
 
     - name: Upload build artifact
@@ -70,8 +68,8 @@ jobs:
       with:
         path: artifacts
 
-    - name: Copy SCHEMA.sql for standalone download
-      run: cp schemas/init.sql SCHEMA.sql
+    - name: Copy standalone schema for download
+      run: cp server/migrations/sql/0001_init.sql SCHEMA.sql
 
     - name: Create GitHub Release
       uses: softprops/action-gh-release@v2