feat(core): enable two step journal by default (#13283)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **New Features**
* The journal confirmation flow is now always enabled when creating or
opening journals across all platforms.

* **Refactor**
* Removed the two-step journal confirmation feature flag and all related
conditional logic.
* Simplified journal navigation and creation flows for a more consistent
user experience.

* **Chores**
* Cleaned up unused components and imports related to the removed
feature flag.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/core/src/modules/feature-flag/constant.ts

@@ -264,14 +264,6 @@ export const AFFINE_FLAGS = {
     configurable: isCanaryBuild,
     defaultState: false,
   },
-  enable_two_step_journal_confirmation: {
-    category: 'affine',
-    displayName: 'Enable Two Step Journal Confirmation',
-    description:
-      'When enabled, you must confirm the journal before you can create a new journal.',
-    configurable: isCanaryBuild,
-    defaultState: isCanaryBuild,
-  },
 } satisfies { [key in string]: FlagInfo };
 
 // oxlint-disable-next-line no-redeclare