notes: color leaves the model, the wire and all three surfaces

Step 3 of M315, and the destructive half. Steps 1 and 2 stopped every read of
this field: a card is one neutral surface per theme, and the only coloured
thing on a board is a tag. What was left was a column written by a picker and
read by nothing.

Rule 22 — the old path comes out completely. No flag, no fallback, no
"override if set".

Server: the column, the `?color=` facet, the create/update/serialise paths,
the sync assignment, the front-matter line, and Keep's colour map. Alembic
0029 drops it and sweeps `"color"` out of stored saved-filter params — a view
that silently filtered on a field the app no longer has would return nothing
and never say why. That sweep is Python, not `params::jsonb - 'color'`,
because Postgres has no try-cast and one malformed blob would abort a
migration that is running over somebody's saved views.

`NOTE_COLORS` moves from `models/note.py` to `colors.py`. A palette defined on
the model that lost one is an invitation to put the column back; labels still
name a colour, so the vocabulary belongs where the normalizer already is.

Core: the field, the facet, the `NoteCreateInput`, and every read and write in
store/push/pull. Local schema v9 drops the column and does the same
saved-filter sweep, guarded on `json_valid` so a corrupt blob loses a key
rather than becoming NULL. The uniffi layer drops `NoteEdit::Color` and
`NoteDraft.color` with it.

Web: `ColorPicker.vue`, the per-card swatch popover and its stylesheet rule,
the FilterBar colour row, the facet in the query round-trip, and the colour
half of the editor's baseline-and-save. Android: the `ColorSheet`, the
`Picker.COLOR` case, the toolbar's swatch dot, `EditorAction.SetColor`.

## The protocol: v4, and the floor deliberately stays at 3

Checked against `compat.rs` and the push handler rather than trusting the
`#[serde(default)]` annotation, because the v2 precedent points the other way:
v2 dropped `kind` and `title` and DID raise both floors, on the rule that
dropping a field a client sends and expects back is breaking.

`color` fails the second half of that test. A v3 client reading a v4 note gets
`"default"` from its own serde default and draws the colour it derives
locally — the board it drew yesterday. A v3 client pushing `color` has the key
ignored, since `_assign_note_fields` reads its payload key by key and never
validates the shape. Neither direction errors and neither shows anything
wrong. `title` was the note's NAME; this is a field that no longer renders.

So `SYNC_PROTOCOL_VERSION` and `CLIENT_PROTOCOL_VERSION` go to 4, and both
floors stay at 3. `docs/sync.md` carries the reasoning and the per-version
history, and its push example is brought back in line — it still listed
`title`, `kind` and `items`, all gone before this.

Import stays tolerant: a pre-M315 export or a Keep takeout carrying `color:`
imports fine, the key simply read past. Old exports must still import.

#3041

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

frontend/src/components/NoteCard.vue

@@ -1,14 +1,7 @@
 <script setup lang="ts">
-import { computed, onBeforeUnmount, ref, watch } from "vue";
+import { computed, ref, watch } from "vue";
 import { useNotesStore } from "../stores/notes";
-import {
-  NOTE_CARD_SURFACE,
-  NOTE_COLOR_KEYS,
-  NOTE_COLOR_LABELS,
-  NOTE_SWATCH_CLASSES,
-  labelChipClasses,
-  type NoteColor,
-} from "../notes/colors";
+import { NOTE_CARD_SURFACE, labelChipClasses } from "../notes/colors";
 import type { Note } from "../stores/notes";
 import Icon from "./Icon.vue";
 import LinkPreview from "./LinkPreview.vue";
@@ -206,27 +199,6 @@ const tagColors = computed<Record<string, string>>(() => {
   return map;
 });
 
-// Per-card color popover (recolor without opening the editor).
-const colorOpen = ref(false);
-
-function swatch(color: string): string {
-  return NOTE_SWATCH_CLASSES[color as NoteColor] ?? NOTE_SWATCH_CLASSES.default;
-}
-
-function pickColor(color: NoteColor) {
-  colorOpen.value = false;
-  void notes.setColor(props.note.id, color);
-}
-
-function onDocMousedown(e: MouseEvent) {
-  if (colorOpen.value && root.value && !root.value.contains(e.target as Node)) colorOpen.value = false;
-}
-// Only listen for outside clicks while the popover is actually open.
-watch(colorOpen, (open) => {
-  if (open) document.addEventListener("mousedown", onDocMousedown);
-  else document.removeEventListener("mousedown", onDocMousedown);
-});
-onBeforeUnmount(() => document.removeEventListener("mousedown", onDocMousedown));
 </script>
 
 <template>
@@ -469,19 +441,6 @@ onBeforeUnmount(() => document.removeEventListener("mousedown", onDocMousedown))
           </button>
         </template>
         <template v-else>
-          <button
-            type="button"
-            class="icon-btn"
-            title="Change color"
-            aria-label="Change color"
-            :aria-expanded="colorOpen"
-            @click.stop="colorOpen = !colorOpen"
-          >
-            <span
-              class="h-4 w-4 rounded-full border border-black/10 dark:border-white/20"
-              :class="swatch(note.color)"
-            ></span>
-          </button>
           <button
             type="button"
             class="icon-btn"
@@ -512,24 +471,6 @@ onBeforeUnmount(() => document.removeEventListener("mousedown", onDocMousedown))
             <Icon name="trash" />
           </button>
         </template>
-
-        <!-- Inside the action set rather than beside it, so it follows the set to
-             whichever corner or footer the device put it in. -->
-        <div
-          v-if="colorOpen"
-          class="note-swatches flex w-40 flex-wrap gap-1.5 rounded-lg border border-neutral-200 bg-white p-2 shadow-lg dark:border-neutral-700 dark:bg-neutral-800"
-        >
-          <button
-            v-for="key in NOTE_COLOR_KEYS"
-            :key="key"
-            type="button"
-            :title="NOTE_COLOR_LABELS[key]"
-            :aria-label="NOTE_COLOR_LABELS[key]"
-            class="h-6 w-6 rounded-full border border-black/10 transition hover:scale-110 focus:outline-none focus-visible:ring-2 focus-visible:ring-brand"
-            :class="[NOTE_SWATCH_CLASSES[key], note.color === key ? 'ring-2 ring-brand' : '']"
-            @click.stop="pickColor(key)"
-          />
-        </div>
       </div>
     </div>
   </div>