Track deploy/mysql/init.sql so fresh deployments initialize the database

The blanket *.sql ignore rule (meant for database dumps) also excluded
deploy/mysql/init.sql, so it was never committed. On a fresh clone the
compose bind mount resolves to a missing file, MySQL skips schema
initialization, and every database-backed page throws.

.gitignore

@@ -41,6 +41,7 @@ app/storage/latex/*
 
 # Database dumps
 *.sql
+!deploy/mysql/init.sql
 backup/
 
 # Temporary files