Merge tasks into notes: a task is just a note with task attributes

A task is now a note with status/priority/due_date columns set (status IS NOT NULL).
This eliminates the separate tasks table, companion note system, cascade deletes,
bidirectional title sync, and _skip_cascade flags.

Migration (0004):
- Add status, priority, due_date columns to notes table
- Migrate task data from companion notes and orphan tasks
- Drop tasks table and old enum types

Backend:
- models/note.py: Add TaskStatus/TaskPriority enums, task columns, is_task property
- models/task.py: Deleted (merged into note.py)
- models/__init__.py: Re-export enums from note.py, remove Task import
- services/notes.py: Remove companion/cascade logic, add is_task filter,
  convert_note_to_task, convert_task_to_note, simplified backlinks
- services/tasks.py: Rewritten as thin wrappers around notes service
- routes/notes.py: Add is_task filter (default false), task fields in CRUD,
  convert-to-note endpoint
- routes/tasks.py: description→body (with fallback), remove note_id filter

Frontend:
- types/note.ts: Add TaskStatus, TaskPriority, task fields to Note interface
- types/task.ts: Task is now a re-export alias for Note
- stores/notes.ts: Simplify convertToTask, add convertToNote
- stores/tasks.ts: description→body in createTask/updateTask
- TaskEditorView: description→body, remove companion note UI
- TaskViewerView: description→body, remove companion note link, add Convert to Note
- NoteViewerView: Remove companion task UI, simplify convert-to-task
- TaskCard: description→body, non-null assertions for status/priority

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/views/TaskEditorView.vue

@@ -6,9 +6,7 @@ import { useNotesStore } from "@/stores/notes";
 import { useToastStore } from "@/stores/toast";
 import { renderMarkdown } from "@/utils/markdown";
 import { useAutocomplete } from "@/composables/useAutocomplete";
-import { apiGet } from "@/api/client";
 import type { TaskStatus, TaskPriority } from "@/types/task";
-import type { Note } from "@/types/note";
 import MarkdownToolbar from "@/components/MarkdownToolbar.vue";
 
 const route = useRoute();
@@ -18,12 +16,10 @@ const notesStore = useNotesStore();
 const toast = useToastStore();
 
 const title = ref("");
-const description = ref("");
+const body = ref("");
 const status = ref<TaskStatus>("todo");
 const priority = ref<TaskPriority>("none");
 const dueDate = ref("");
-const noteId = ref<number | null>(null);
-const companionNote = ref<Note | null>(null);
 const dirty = ref(false);
 const saving = ref(false);
 const showPreview = ref(false);
@@ -34,7 +30,7 @@ const taskId = computed(() =>
 );
 const isEditing = computed(() => taskId.value !== null);
 
-const renderedPreview = computed(() => renderMarkdown(description.value));
+const renderedPreview = computed(() => renderMarkdown(body.value));
 
 // Autocomplete
 const {
@@ -47,10 +43,10 @@ const {
   accept: acAccept,
   dismiss: acDismiss,
   onKeydown: acOnKeydown,
-} = useAutocomplete(textareaRef, description, (q) => notesStore.fetchAllTags(q));
+} = useAutocomplete(textareaRef, body, (q) => notesStore.fetchAllTags(q));
 
 let savedTitle = "";
-let savedDescription = "";
+let savedBody = "";
 let savedStatus: TaskStatus = "todo";
 let savedPriority: TaskPriority = "none";
 let savedDueDate = "";
@@ -58,7 +54,7 @@ let savedDueDate = "";
 function markDirty() {
   dirty.value =
     title.value !== savedTitle ||
-    description.value !== savedDescription ||
+    body.value !== savedBody ||
     status.value !== savedStatus ||
     priority.value !== savedPriority ||
     dueDate.value !== savedDueDate;
@@ -71,7 +67,7 @@ function autoGrow() {
   el.style.height = Math.max(el.scrollHeight, 200) + "px";
 }
 
-function onDescriptionInput() {
+function onBodyInput() {
   markDirty();
   autoGrow();
   detectTrigger();
@@ -93,10 +89,10 @@ function insertAtCursor(before: string, after: string, placeholder: string) {
     el.focus();
     const start = el.selectionStart;
     const end = el.selectionEnd;
-    const selected = description.value.slice(start, end);
+    const selected = body.value.slice(start, end);
     const insert = selected || placeholder;
-    description.value =
-      description.value.slice(0, start) + before + insert + after + description.value.slice(end);
+    body.value =
+      body.value.slice(0, start) + before + insert + after + body.value.slice(end);
     markDirty();
     nextTick(() => {
       const newStart = start + before.length;
@@ -113,24 +109,15 @@ onMounted(async () => {
     await store.fetchTask(taskId.value);
     if (store.currentTask) {
       title.value = store.currentTask.title;
-      description.value = store.currentTask.description;
-      status.value = store.currentTask.status;
-      priority.value = store.currentTask.priority;
+      body.value = store.currentTask.body;
+      status.value = store.currentTask.status as TaskStatus;
+      priority.value = store.currentTask.priority as TaskPriority;
       dueDate.value = store.currentTask.due_date || "";
-      noteId.value = store.currentTask.note_id;
       savedTitle = title.value;
-      savedDescription = description.value;
+      savedBody = body.value;
       savedStatus = status.value;
       savedPriority = priority.value;
       savedDueDate = dueDate.value;
-
-      if (noteId.value) {
-        try {
-          companionNote.value = await apiGet<Note>(`/api/notes/${noteId.value}`);
-        } catch {
-          companionNote.value = null;
-        }
-      }
     }
   }
   nextTick(autoGrow);
@@ -142,7 +129,7 @@ async function save() {
   try {
     const data = {
       title: title.value,
-      description: description.value,
+      body: body.value,
       status: status.value,
       priority: priority.value,
       due_date: dueDate.value || null,
@@ -150,7 +137,7 @@ async function save() {
     if (isEditing.value) {
       await store.updateTask(taskId.value!, data);
       savedTitle = title.value;
-      savedDescription = description.value;
+      savedBody = body.value;
       savedStatus = status.value;
       savedPriority = priority.value;
       savedDueDate = dueDate.value;
@@ -254,10 +241,10 @@ onUnmounted(() => window.removeEventListener("beforeunload", onBeforeUnload));
     <div class="textarea-wrapper" v-show="!showPreview">
       <textarea
         ref="textareaRef"
-        v-model="description"
+        v-model="body"
         placeholder="Describe this task... Use #tags inline"
         class="body-input"
-        @input="onDescriptionInput"
+        @input="onBodyInput"
         @keydown="onTextareaKeydown"
         @blur="onTextareaBlur"
       ></textarea>
@@ -314,13 +301,6 @@ onUnmounted(() => window.removeEventListener("beforeunload", onBeforeUnload));
       </div>
     </div>
 
-    <div v-if="companionNote" class="field companion-note">
-      <label>Companion Note</label>
-      <router-link :to="`/notes/${companionNote.id}`" class="note-link">
-        {{ companionNote.title || "Untitled" }}
-      </router-link>
-    </div>
-
     <!-- Delete confirmation -->
     <teleport to="body">
       <div v-if="showDeleteConfirm" class="modal-overlay" @click="showDeleteConfirm = false">
@@ -476,19 +456,6 @@ onUnmounted(() => window.removeEventListener("beforeunload", onBeforeUnload));
   color: var(--color-text);
   font-size: 0.9rem;
 }
-.companion-note {
-  flex-direction: row;
-  align-items: center;
-  gap: 0.5rem;
-}
-.note-link {
-  color: var(--color-primary);
-  text-decoration: none;
-  font-size: 0.9rem;
-}
-.note-link:hover {
-  text-decoration: underline;
-}
 .modal-overlay {
   position: fixed;
   inset: 0;