refactor: move doc-title and ai-chat-block components (#10316)

### TL;DR
Moved doc title and AI chat block components to more appropriate locations while removing unused backlink functionality.

### What changed?
- Relocated doc title component from presets to affine-components
- Moved AI chat block from presets/blocks to blocks directory
- Removed unused backlink-related code and components
- Updated imports across files to reference new component locations
- Consolidated AI-related exports through a single entry point

### How to test?
1. Verify doc title still renders correctly in documents
2. Confirm AI chat functionality works as expected
3. Check that no backlink-related features are accessible
4. Ensure all AI features continue to work through the new import paths

### Why make this change?
This reorganization improves code organization by:
- Placing components closer to their related functionality
- Removing dead/unused code around backlinks
- Simplifying the import structure for AI-related features
- Making the codebase more maintainable by consolidating related components

blocksuite/blocks/src/effects.ts

@@ -22,6 +22,7 @@ import { effects as componentCaptionEffects } from '@blocksuite/affine-component
 import { effects as componentColorPickerEffects } from '@blocksuite/affine-components/color-picker';
 import { effects as componentContextMenuEffects } from '@blocksuite/affine-components/context-menu';
 import { effects as componentDatePickerEffects } from '@blocksuite/affine-components/date-picker';
+import { effects as componentDocTitleEffects } from '@blocksuite/affine-components/doc-title';
 import { effects as componentDropIndicatorEffects } from '@blocksuite/affine-components/drop-indicator';
 import { effects as componentEmbedCardModalEffects } from '@blocksuite/affine-components/embed-card-modal';
 import { FilterableListComponent } from '@blocksuite/affine-components/filterable-list';
@@ -213,6 +214,7 @@ export function effects() {
   componentAiItemEffects();
   componentColorPickerEffects();
   componentEmbedCardModalEffects();
+  componentDocTitleEffects();
 
   widgetScrollAnchoringEffects();
   widgetMobileToolbarEffects();

blocksuite/blocks/src/index.ts

@@ -58,6 +58,10 @@ export {
   type MenuOptions,
   onMenuOpen,
 } from '@blocksuite/affine-components/context-menu';
+export {
+  DocTitle,
+  getDocTitleByEditorHost,
+} from '@blocksuite/affine-components/doc-title';
 export {
   HoverController,
   whenHover,