stacker sync does not persist config_contract to project_app table

[vsilent]

Bug Description

stacker sync does not persist the config_contract section from stacker.yml to the project_app.config_contract database column. The field remains NULL for all project apps after sync.

Steps to Reproduce

1. Create a stacker.yml with a populated config_contract section:

   config_contract:
     services:
       app:
         fields:
           SECRET_KEY:
             mutability: generated
             type: alphanumeric
             length: 32
             display: password

2. Run stacker sync

3. Query the database:

   SELECT app_code, config_contract FROM project_app WHERE project_id = <id>;

4. Observe that config_contract IS NULL for all rows

Expected Behavior

Per the STACKER_SYNC_PLAN.md, config_contract should be persisted:

Project app configuration is stored in:

• project_app.environment
• project_app.ports
• project_app.volumes
• project_app.config_files
• project_app.config_contract ← Should be written

The regression tests also specify:

"config contracts not being lost during sync"

Actual Behavior

config_contract is NULL in the project_app table after stacker sync.

Root Cause

In src/project_app/sync.rs, the build_project_app() function constructs a ProjectApp but never sets the config_contract field:

fn build_project_app(...) -> models::ProjectApp {
    let mut project_app = models::ProjectApp::new(...);
    
    project_app.environment = ...;
    project_app.ports = ...;
    project_app.volumes = ...;
    project_app.domain = ...;
    project_app.restart_policy = ...;
    project_app.command = ...;
    project_app.entrypoint = ...;
    project_app.networks = ...;
    // config_contract is NEVER SET ← BUG
    project_app
}

Workaround

stacker submit (marketplace submission) DOES persist config_contract as part of the template payload. The relevant code in src/console/commands/cli/submit.rs:

let config_contract = serde_json::to_value(&config.config_contract)?;
if config_contract
    .get("services")
    .and_then(|services| services.as_object())
    .is_some_and(|services| !services.is_empty())
{
    body["config_contract"] = config_contract;
}

Impact

• Stack Builder UI cannot display config contract fields for synced projects
• Developers must use stacker submit to persist config contracts
• The sync plan's acceptance criteria is not met

Environment

• Stacker CLI version: 0.3.3
• Command: stacker sync --json

Additional Context

The STACKER_SYNC_PLAN.md explicitly lists config_contract as a field that should be synchronized:

Store in PostgreSQL
Store non-secret, declarative configuration:

• app image;
• app name and code;
• non-secret environment values;
• ports;
• volumes;
• domains;
• restart policy;
• config contract; ← Listed as required

The plan also includes this regression test:

"config contracts not being lost during sync"