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

server/migrations/seed/GachaDemo.sql

@@ -0,0 +1,102 @@
+BEGIN;
+
+-- Start Normal Demo
+INSERT INTO gacha_shop (min_gr, min_hr, name, url_banner, url_feature, url_thumbnail, wide, recommended, gacha_type, hidden)
+    VALUES (0, 0, 'Normal Demo',
+    'http://img4.imagetitan.com/img4/QeRWNAviFD8UoTx/26/26_template_innerbanner.png',
+    'http://img4.imagetitan.com/img4/QeRWNAviFD8UoTx/26/26_template_feature.png',
+    'http://img4.imagetitan.com/img4/small/26/26_template_outerbanner.png',
+    false, false, 0, false);
+
+-- Create two different 'rolls', the first rolls once for 1z, the second rolls eleven times for 10z
+INSERT INTO gacha_entries (gacha_id, entry_type, item_type, item_number, item_quantity, weight, rarity, rolls, daily_limit, frontier_points)
+VALUES
+    ((SELECT id FROM gacha_shop ORDER BY id DESC LIMIT 1), 0, 10, 1, 0, 0, 0, 1, 0, 0),
+    ((SELECT id FROM gacha_shop ORDER BY id DESC LIMIT 1), 1, 10, 10, 0, 0, 0, 11, 0, 0);
+
+-- Creates a prize of 1z with a weighted chance of 100
+INSERT INTO gacha_entries (gacha_id, entry_type, item_type, item_number, item_quantity, weight, rarity, rolls, daily_limit, frontier_points)
+    VALUES ((SELECT id FROM gacha_shop ORDER BY id DESC LIMIT 1), 100, 0, 0, 0, 100, 0, 0, 0, 0);
+INSERT INTO gacha_items (entry_id, item_type, item_id, quantity)
+    VALUES ((SELECT id FROM gacha_entries ORDER BY id DESC LIMIT 1), 10, 1, 0);
+
+-- Creates a prize of 2z with a weighted chance of 70
+INSERT INTO gacha_entries (gacha_id, entry_type, item_type, item_number, item_quantity, weight, rarity, rolls, daily_limit, frontier_points)
+    VALUES ((SELECT id FROM gacha_shop ORDER BY id DESC LIMIT 1), 100, 0, 0, 0, 70, 1, 0, 0, 0);
+INSERT INTO gacha_items (entry_id, item_type, item_id, quantity)
+    VALUES ((SELECT id FROM gacha_entries ORDER BY id DESC LIMIT 1), 10, 2, 0);
+
+-- Creates a prize of 3z with a weighted chance of 10
+INSERT INTO gacha_entries (gacha_id, entry_type, item_type, item_number, item_quantity, weight, rarity, rolls, daily_limit, frontier_points)
+    VALUES ((SELECT id FROM gacha_shop ORDER BY id DESC LIMIT 1), 100, 0, 0, 0, 10, 2, 0, 0, 0);
+INSERT INTO gacha_items (entry_id, item_type, item_id, quantity)
+    VALUES ((SELECT id FROM gacha_entries ORDER BY id DESC LIMIT 1), 10, 3, 0);
+-- End Normal Demo
+
+-- Start Step-Up Demo
+INSERT INTO gacha_shop (min_gr, min_hr, name, url_banner, url_feature, url_thumbnail, wide, recommended, gacha_type, hidden)
+VALUES (0, 0, 'Step-Up Demo', '', '', '', false, false, 1, false);
+
+-- Create two 'steps', the first costs 1z, the second costs 2z
+-- The first step has zero rolls so it will only give the prizes directly linked to the entry ID, being 1z
+INSERT INTO gacha_entries (gacha_id, entry_type, item_type, item_number, item_quantity, weight, rarity, rolls, daily_limit, frontier_points)
+    VALUES ((SELECT id FROM gacha_shop ORDER BY id DESC LIMIT 1), 0, 10, 1, 0, 0, 0, 0, 0, 0);
+INSERT INTO gacha_items (entry_id, item_type, item_id, quantity)
+    VALUES ((SELECT id FROM gacha_entries ORDER BY id DESC LIMIT 1), 10, 1, 0);
+
+-- The second step has one roll on the random prize list as will as the direct prize, being 3z
+INSERT INTO gacha_entries (gacha_id, entry_type, item_type, item_number, item_quantity, weight, rarity, rolls, daily_limit, frontier_points)
+    VALUES ((SELECT id FROM gacha_shop ORDER BY id DESC LIMIT 1), 1, 10, 2, 0, 0, 0, 1, 0, 0);
+INSERT INTO gacha_items (entry_id, item_type, item_id, quantity)
+    VALUES ((SELECT id FROM gacha_entries ORDER BY id DESC LIMIT 1), 10, 3, 0);
+
+-- Set up two random prizes, the first gives 1z, the second gives 2z
+INSERT INTO gacha_entries (gacha_id, entry_type, item_type, item_number, item_quantity, weight, rarity, rolls, daily_limit, frontier_points)
+    VALUES ((SELECT id FROM gacha_shop ORDER BY id DESC LIMIT 1), 100, 0, 0, 0, 100, 0, 0, 0, 0);
+INSERT INTO gacha_items (entry_id, item_type, item_id, quantity)
+    VALUES ((SELECT id FROM gacha_entries ORDER BY id DESC LIMIT 1), 10, 1, 0);
+
+INSERT INTO gacha_entries (gacha_id, entry_type, item_type, item_number, item_quantity, weight, rarity, rolls, daily_limit, frontier_points)
+    VALUES ((SELECT id FROM gacha_shop ORDER BY id DESC LIMIT 1), 100, 0, 0, 0, 90, 1, 0, 0, 0);
+INSERT INTO gacha_items (entry_id, item_type, item_id, quantity)
+    VALUES ((SELECT id FROM gacha_entries ORDER BY id DESC LIMIT 1), 10, 2, 0);
+-- End Step-Up Demo
+
+-- Start Box Demo
+INSERT INTO gacha_shop (min_gr, min_hr, name, url_banner, url_feature, url_thumbnail, wide, recommended, gacha_type, hidden)
+VALUES (0, 0, 'Box Demo', '', '', '', false, false, 4, false);
+
+-- Create two different 'rolls', the first rolls once for 1z, the second rolls twice for 2z
+INSERT INTO gacha_entries (gacha_id, entry_type, item_type, item_number, item_quantity, weight, rarity, rolls, daily_limit, frontier_points)
+VALUES
+    ((SELECT id FROM gacha_shop ORDER BY id DESC LIMIT 1), 0, 10, 1, 0, 0, 0, 1, 0, 0),
+    ((SELECT id FROM gacha_shop ORDER BY id DESC LIMIT 1), 1, 10, 2, 0, 0, 0, 2, 0, 0);
+
+-- Create five different 'Box' items, weight is always 0 for these
+INSERT INTO gacha_entries (gacha_id, entry_type, item_type, item_number, item_quantity, weight, rarity, rolls, daily_limit, frontier_points)
+    VALUES ((SELECT id FROM gacha_shop ORDER BY id DESC LIMIT 1), 100, 0, 0, 0, 0, 0, 0, 0, 0);
+INSERT INTO gacha_items (entry_id, item_type, item_id, quantity)
+    VALUES ((SELECT id FROM gacha_entries ORDER BY id DESC LIMIT 1), 10, 1, 0);
+
+INSERT INTO gacha_entries (gacha_id, entry_type, item_type, item_number, item_quantity, weight, rarity, rolls, daily_limit, frontier_points)
+    VALUES ((SELECT id FROM gacha_shop ORDER BY id DESC LIMIT 1), 100, 0, 0, 0, 0, 0, 0, 0, 0);
+INSERT INTO gacha_items (entry_id, item_type, item_id, quantity)
+    VALUES ((SELECT id FROM gacha_entries ORDER BY id DESC LIMIT 1), 10, 1, 0);
+
+INSERT INTO gacha_entries (gacha_id, entry_type, item_type, item_number, item_quantity, weight, rarity, rolls, daily_limit, frontier_points)
+    VALUES ((SELECT id FROM gacha_shop ORDER BY id DESC LIMIT 1), 100, 0, 0, 0, 0, 0, 0, 0, 0);
+INSERT INTO gacha_items (entry_id, item_type, item_id, quantity)
+    VALUES ((SELECT id FROM gacha_entries ORDER BY id DESC LIMIT 1), 10, 1, 0);
+
+INSERT INTO gacha_entries (gacha_id, entry_type, item_type, item_number, item_quantity, weight, rarity, rolls, daily_limit, frontier_points)
+    VALUES ((SELECT id FROM gacha_shop ORDER BY id DESC LIMIT 1), 100, 0, 0, 0, 0, 0, 0, 0, 0);
+INSERT INTO gacha_items (entry_id, item_type, item_id, quantity)
+    VALUES ((SELECT id FROM gacha_entries ORDER BY id DESC LIMIT 1), 10, 2, 0);
+
+INSERT INTO gacha_entries (gacha_id, entry_type, item_type, item_number, item_quantity, weight, rarity, rolls, daily_limit, frontier_points)
+    VALUES ((SELECT id FROM gacha_shop ORDER BY id DESC LIMIT 1), 100, 0, 0, 0, 0, 0, 0, 0, 0);
+INSERT INTO gacha_items (entry_id, item_type, item_id, quantity)
+    VALUES ((SELECT id FROM gacha_entries ORDER BY id DESC LIMIT 1), 10, 3, 0);
+-- End Box Demo
+
+END;