fix: schema compilation wasn't adding ON CLUSTER, causing false diffs

[kirillkuts]

When comparing schemas, we were getting false positives about cluster changes even though nothing actually changed.

The problem:

• When we compile schema from files, we weren't adding ON CLUSTER clauses
• When we extract schema from the database, we DO add ON CLUSTER clauses
• So diff thinks the cluster name changed every time, even when it didn't

Reproduction steps:

mkdir my-clickhouse-project
cd my-clickhouse-project
housekeeper init
echo "CREATE DATABASE \`analytics\` ENGINE = Atomic COMMENT 'Analytics database';" > db/main.sql
housekeeper diff
housekeeper diff

Expected result:
Second housekeeper diff finds no differences

Actual result:
Second housekeeper diff fails with cannot change cluster from 'cluster' to '': cluster configuration changes not supported error

The fix:
Moved the InjectOnCluster function to pkg/parser so both paths can use it:

• pkg/parser/utils.go - moved InjectOnCluster to a new file inside parser package
• pkg/clickhouse/dump_schema.go - now calls parser.InjectOnCluster
• pkg/cmd/util.go - compileProjectSchema now also calls parser.InjectOnCluster when compiling schema

Now both schema extraction and compilation add ON CLUSTER the same way, so we don't get fake diffs anymore

Additional impact:

• Migrations will automatically include ON CLUSTER into statements