Fix SQL schema issues across all database engines

- Increase password column from varchar(64) to varchar(255) to
  prevent silent truncation of encrypted passwords
- Add missing UNIQUE constraint on iid in MySQL
- Add missing IX_ident_switch_iid index in PostgreSQL
- Remove deprecated int display width in MySQL (int(10) -> int)
- Fix trailing comma syntax error in SQLite 2018121800 migration
- Normalize indentation across all initial SQL files
- Add migration 2026021000 for all engines to fix existing installs

SQL/postgres/2026021000.sql

@@ -0,0 +1,4 @@
+ALTER TABLE ident_switch
+	ALTER COLUMN password TYPE varchar(255);
+
+CREATE INDEX IF NOT EXISTS IX_ident_switch_iid ON ident_switch(iid);