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/sqlite.initial.sql

@@ -15,7 +15,7 @@ CREATE TABLE ident_switch
 	username
 		varchar(64),
 	password
-		varchar(64),
+		varchar(255),
 	imap_host
 		varchar(64),
 	imap_port
@@ -49,4 +49,4 @@ CREATE TABLE ident_switch
 	UNIQUE (user_id, label)
 );
 CREATE INDEX IX_ident_switch_user_id ON ident_switch(user_id);
-CREATE INDEX IX_ident_switch_iid on ident_switch(iid);
+CREATE INDEX IX_ident_switch_iid ON ident_switch(iid);