labels: per-label color

Give labels a color (migration 0011 adds labels.color, server_default
'default' so existing labels keep the neutral chip). The PATCH endpoint now
updates name and/or color; note serialization carries each label's color.
Frontend: a swatch picker per label in the Edit-labels modal, colored chips
on cards + in the editor (LABEL_CHIP_CLASSES), and a color dot on each
sidebar label. Reuses the note color vocabulary. (Graph node coloring rides
this in the graph-liveliness task.)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FRgehjoz7Yv8LkUfADxACm

frontend/src/components/NoteEditor.vue

@@ -9,7 +9,7 @@ import LabelPicker from "./LabelPicker.vue";
 import NoteChecklist from "./NoteChecklist.vue";
 import { fromLocalInput, toLocalInput } from "../notes/datetime";
 import type { Note, NoteLabel } from "../stores/notes";
-import type { NoteColor } from "../notes/colors";
+import { LABEL_CHIP_CLASSES, type NoteColor } from "../notes/colors";
 
 const props = defineProps<{ note: Note }>();
 const emit = defineEmits<{ (e: "close"): void; (e: "navigate", id: string): void }>();
@@ -176,6 +176,10 @@ async function removeLabel(id: string) {
   await onLabelsChange(labelList.value.filter((lb) => lb.id !== id));
 }
 
+function labelChip(color: string): string {
+  return LABEL_CHIP_CLASSES[color as NoteColor] ?? LABEL_CHIP_CLASSES.default;
+}
+
 async function toggleKind() {
   if (liveNote.value.kind === "list") {
     await notes.setKind(props.note.id, "text");
@@ -315,7 +319,8 @@ async function act(fn: () => Promise<void>) {
           <span
             v-for="lb in labelList"
             :key="lb.id"
-            class="inline-flex items-center gap-1 rounded-full bg-black/5 px-2 py-0.5 text-xs text-neutral-600 dark:bg-white/10 dark:text-neutral-300"
+            class="inline-flex items-center gap-1 rounded-full px-2 py-0.5 text-xs"
+            :class="labelChip(lb.color)"
           >
             {{ lb.name }}
             <button