Fix project/milestone association and redesign AppHeader navigation

Backend:
- routes/tasks.py: POST + PUT were silently dropping project_id,
  milestone_id, parent_id from request body — root cause of association
  not saving from the task editor
- routes/tasks.py: GET /api/tasks/:id now includes parent_title in
  response (secondary lookup when parent_id is set)
- routes/notes.py: add PATCH /api/notes/:id for partial updates (used
  by sub-task status toggle; PUT already existed but PATCH was missing)
- routes/projects.py: GET /api/projects/:id/notes now fetches milestone
  IDs and passes them via milestone_ids so tasks assigned to a milestone
  (but lacking project_id) are included in the project view
- services/notes.py: create_note() auto-sets project_id from milestone
  when milestone_id is provided and project_id is omitted; list_notes()
  gains milestone_ids param — when combined with project_id uses OR
  condition (project_id=X OR milestone_id IN (...))

Frontend:
- NoteEditorView: add MilestoneSelector; milestone resets when project
  changes; all save paths (save/create/auto-save) include milestone_id
- stores/notes.ts: add milestone_id to createNote + updateNote types
- TaskEditorView: sub-tasks now inherit milestone_id from parent task
- AppHeader: three-zone layout — brand left, Notes/Projects/Tasks/Chat
  centered (absolute positioning), right rail with status/theme/? and
  gear dropdown containing Settings/Users/Logs; mobile dropdown unchanged

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

frontend/src/views/NoteEditorView.vue

@@ -11,6 +11,7 @@ import MarkdownToolbar from "@/components/MarkdownToolbar.vue";
 import TiptapEditor from "@/components/TiptapEditor.vue";
 import TagInput from "@/components/TagInput.vue";
 import ProjectSelector from "@/components/ProjectSelector.vue";
+import MilestoneSelector from "@/components/MilestoneSelector.vue";
 
 const route = useRoute();
 const router = useRouter();
@@ -21,6 +22,7 @@ const title = ref("");
 const body = ref("");
 const tags = ref<string[]>([]);
 const projectId = ref<number | null>(null);
+const milestoneId = ref<number | null>(null);
 const dirty = ref(false);
 const saving = ref(false);
 const showPreview = ref(false);
@@ -139,13 +141,15 @@ let savedTitle = "";
 let savedBody = "";
 let savedTags: string[] = [];
 let savedProjectId: number | null = null;
+let savedMilestoneId: number | null = null;
 
 function markDirty() {
   dirty.value =
     title.value !== savedTitle ||
     body.value !== savedBody ||
     JSON.stringify(tags.value) !== JSON.stringify(savedTags) ||
-    projectId.value !== savedProjectId;
+    projectId.value !== savedProjectId ||
+    milestoneId.value !== savedMilestoneId;
 }
 
 function onBodyUpdate(newVal: string) {
@@ -161,10 +165,12 @@ onMounted(async () => {
       body.value = store.currentNote.body;
       tags.value = [...(store.currentNote.tags || [])];
       projectId.value = store.currentNote.project_id ?? null;
+      milestoneId.value = store.currentNote.milestone_id ?? null;
       savedTitle = title.value;
       savedBody = body.value;
       savedTags = [...tags.value];
       savedProjectId = projectId.value;
+      savedMilestoneId = milestoneId.value;
     }
   }
 });
@@ -179,11 +185,13 @@ async function save() {
         body: body.value,
         tags: tags.value,
         project_id: projectId.value,
+        milestone_id: milestoneId.value,
       });
       savedTitle = title.value;
       savedBody = body.value;
       savedTags = [...tags.value];
       savedProjectId = projectId.value;
+      savedMilestoneId = milestoneId.value;
       dirty.value = false;
       toast.show("Note saved");
     } else {
@@ -192,6 +200,7 @@ async function save() {
         body: body.value,
         tags: tags.value,
         project_id: projectId.value,
+        milestone_id: milestoneId.value,
       });
       dirty.value = false;
       toast.show("Note created");
@@ -232,11 +241,12 @@ async function autoSave() {
   if (!isEditing.value || !dirty.value || saving.value) return;
   saving.value = true;
   try {
-    await store.updateNote(noteId.value!, { title: title.value, body: body.value, tags: tags.value, project_id: projectId.value } as Record<string, unknown>);
+    await store.updateNote(noteId.value!, { title: title.value, body: body.value, tags: tags.value, project_id: projectId.value, milestone_id: milestoneId.value } as Record<string, unknown>);
     savedTitle = title.value;
     savedBody = body.value;
     savedTags = [...tags.value];
     savedProjectId = projectId.value;
+    savedMilestoneId = milestoneId.value;
     dirty.value = false;
     toast.show("Auto-saved");
   } catch {
@@ -303,7 +313,11 @@ onUnmounted(() => window.removeEventListener("beforeunload", onBeforeUnload));
       <div class="field-row-meta">
         <div class="meta-field">
           <label class="meta-label">Project</label>
-          <ProjectSelector v-model="projectId" @update:modelValue="markDirty" />
+          <ProjectSelector v-model="projectId" @update:modelValue="milestoneId = null; markDirty()" />
+        </div>
+        <div class="meta-field">
+          <label class="meta-label">Milestone</label>
+          <MilestoneSelector :projectId="projectId" v-model="milestoneId" @update:modelValue="markDirty" />
         </div>
       </div>