Improve cache-clear behavior (#17662)
## Cache flush: scope and options
**Scope**
- `cache:flush` only flushes the **cache** Redis (REDIS_URL). It no
longer touches the queue Redis.
**Options**
- **`--namespace`** (optional): Flush one namespace or omit to flush
all. Valid: `module:messaging`, `module:calendar`, `module:workflow`,
`engine:workspace`, `engine:lock`, `engine:health`,
`engine:subscriptions`.
- **`--pattern`** (optional, default `*`): Key pattern inside the chosen
namespace(s).
**Troubleshooting**
- **`cache:flush:verify`**: Inserts keys inside and outside
`engine:workspace`, flushes, and checks only namespace keys are removed
(confirms flush scope).
**Usage**
- `yarn command:prod cache:flush` — flush all **KNOWN** namespaces
- `yarn command:prod cache:flush -n engine:workspace` — flush one
namespace
- `yarn command:prod cache:flush -n engine:workspace -p
"feature-flag:*"` — flush keys matching pattern in given namespace
FYI, existing namespaces:
```
export enum CacheStorageNamespace {
ModuleMessaging = 'module:messaging',
ModuleCalendar = 'module:calendar',
ModuleWorkflow = 'module:workflow',
EngineWorkspace = 'engine:workspace',
EngineLock = 'engine:lock',
EngineHealth = 'engine:health',
EngineSubscriptions = 'engine:subscriptions',
}
```
