feat: full Internal Link Picker with search and type filter

Replace broken ObjectPickerModal and manual modal with proper
InternalLinkPicker component:

- Search field with debounced SearchNodes API calls
- Type tabs: Дело, Заметка, Файл, Секрет (disabled)
- Results list showing title + path, keyboard navigation
- Inserts [Title](verstak://type/id) at cursor position
- No layout breakage — picker is a normal modal via position:fixed
- Escape/Cancel close picker cleanly
- bind:this on NoteEditorPanel → MarkdownEditor.insertText()

Also:
- MarkdownEditor: added public insertText() method + bind:this
- NoteEditorPanel: added bind:this on MarkdownEditor + public insertText()
- Removed manual modal, insertInternalLinkMarkdown(), document.querySelector

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