feat(core): comment panel (#12989)

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

* **New Features**
* Introduced a full-featured document comment system with sidebar for
viewing, filtering, replying, resolving, and managing comments and
replies.
* Added a rich text comment editor supporting editable and read-only
modes.
  * Enabled comment-based navigation and highlighting within documents.
* Integrated comment functionality into the workspace sidebar (excluding
local workspaces).
* Added internationalization support and new UI strings for comment
features.
* Added new feature flag `enable_comment` for toggling comment
functionality.
  * Enhanced editor focus to support comment-related selections.
  * Added snapshot and store helpers for comment content management.
* Implemented backend GraphQL support for comment and reply operations.
* Added services for comment entity management and comment panel
behavior.
* Extended comment configuration to support optional framework
providers.
* Added preview generation from user selections when creating comments.
  * Enabled automatic sidebar opening on new pending comments.
  * Added comment-related query parameter support for navigation.
  * Included inline comment module exports for integration.
* Improved comment provider implementation with full lifecycle
management and UI integration.
* Added comment highlight state tracking and refined selection handling
in inline comments.

* **Style**
* Added comprehensive styles for the comment editor and sidebar
components.

* **Chores**
  * Updated language completeness percentages for multiple locales.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

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Co-authored-by: L-Sun <zover.v@gmail.com>

blocksuite/affine/shared/src/services/feature-flag-service.ts

@@ -21,6 +21,7 @@ export interface BlockSuiteFlags {
   enable_table_virtual_scroll: boolean;
   enable_turbo_renderer: boolean;
   enable_dom_renderer: boolean;
+  enable_comment: boolean;
 }
 
 export class FeatureFlagService extends StoreExtension {
@@ -46,6 +47,7 @@ export class FeatureFlagService extends StoreExtension {
     enable_table_virtual_scroll: false,
     enable_turbo_renderer: false,
     enable_dom_renderer: false,
+    enable_comment: false,
   });
 
   setFlag(key: keyof BlockSuiteFlags, value: boolean) {