Exclude any mutating tools when in read_only mode

[gregnr]

Currently when setting the server to read_only mode, this only applies to database operations:

• execute_sql (by running as read only postgres user)
• apply_migration (by rejecting the tool)

We should change this to also reject the following mutating tools:

• create_project
• pause_project
• restore_project
• deploy_edge_function
• create_branch
• delete_branch
• merge_branch
• reset_branch
• rebase_branch
• update_storage_config

We should also update the readme accordingly.

[diksipav]

Will do this : )