feat: add notes feature and keyboard shortcuts

- Introduced a new Note model in the Prisma schema to support note-taking functionality.
- Updated the HeaderNavigation component to include a link to the new Notes page.
- Implemented keyboard shortcuts for note actions, enhancing user experience and productivity.
- Added dependencies for markdown rendering and formatting tools to support note content.

prisma/schema.prisma

@@ -21,6 +21,7 @@ model User {
   createdAt   DateTime @default(now())
   updatedAt   DateTime @updatedAt
   preferences UserPreferences?
+  notes       Note[]
 
   @@map("users")
 }
@@ -62,6 +63,7 @@ model Tag {
   isPinned     Boolean   @default(false)
   taskTags     TaskTag[]
   primaryTasks Task[]    @relation("PrimaryTag")
+  noteTags     NoteTag[]
 
   @@map("tags")
 }
@@ -121,3 +123,24 @@ model UserPreferences {
 
   @@map("user_preferences")
 }
+
+model Note {
+  id        String   @id @default(cuid())
+  title     String
+  content   String   // Markdown content
+  userId    String
+  createdAt DateTime @default(now())
+  updatedAt DateTime @updatedAt
+  user      User     @relation(fields: [userId], references: [id], onDelete: Cascade)
+  noteTags  NoteTag[]
+}
+
+model NoteTag {
+  noteId String
+  tagId  String
+  tag    Tag    @relation(fields: [tagId], references: [id], onDelete: Cascade)
+  note   Note   @relation(fields: [noteId], references: [id], onDelete: Cascade)
+
+  @@id([noteId, tagId])
+  @@map("note_tags")
+}