copy: the product says "tags" now, and the schema keeps saying Label

Two words for one concept cost real comprehension: over a single exchange
the operator concluded that auto-tagging did not exist (it does, in
`derive.rs`) and that a tag-management view did not exist (it does,
`LabelsModal.vue`). The `#` is how most of these get made, so the `#` wins
the noun.

User-visible strings only, on all three surfaces plus the server's errors.
`Label`, `NoteLabel`, `via_tag`, `label_id`, the tables, `/api/labels` and
the FFI names are all untouched — renaming those touches migrations and the
wire format to buy nothing a reader can see.

Two of these were more than a find-and-replace:

  * Android's `label_from_tag` said "from #tag", sitting beside a chip that
    already renders as `#name`. Once every one of them IS a tag that hint is
    circular. What it actually tells you is that the note's BODY owns this
    one — which is why it alone has no remove cross — so it now says "from
    the text".

  * The web's empty state said "No labels yet — create one above" while
    Android's already mentioned the `#` route. The web now says it too. That
    is the exact fact the operator did not have.

The paired `aria-label`s went with their `title`s; a screen reader saying
"label" while the tooltip says "tag" is the same confusion with a smaller
audience.

Left alone deliberately: `json_error("invalid label")` and
`"label_ids must be a list"` in `notes/__init__.py` name the `?label=` query
parameter and the `label_ids` request field. Those are wire surface, not the
word a person reads.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01K3MMqUtzX1TJgA1oypvm1c

frontend/src/components/AppShell.vue

@@ -441,18 +441,18 @@ async function signOut() {
           </RouterLink>
 
           <div class="mt-3 flex items-center justify-between px-3 pb-1">
-            <span class="text-xs font-semibold uppercase tracking-wide text-neutral-400">Labels</span>
+            <span class="text-xs font-semibold uppercase tracking-wide text-neutral-400">Tags</span>
             <button
               type="button"
               class="text-neutral-400 hover:text-neutral-600 dark:hover:text-neutral-200"
-              title="Edit labels"
-              aria-label="Edit labels"
+              title="Manage tags"
+              aria-label="Manage tags"
               @click="managing = true"
             >
               <Icon name="pencil" />
             </button>
           </div>
-          <p v-if="!labels.items.length" class="px-3 py-1 text-xs text-neutral-400">No labels yet</p>
+          <p v-if="!labels.items.length" class="px-3 py-1 text-xs text-neutral-400">No tags yet</p>
           <RouterLink
             v-for="lb in labels.items"
             :key="lb.id"