v1.47.0: pick a plan you already uploaded

Closes both findings from the v1.46.6 review with one feature, because they are
the same gap seen from two sides. HP-1466-02: a detached plan stayed on disk and
could not be re-attached from the card — the old url is nowhere in the config,
and the backend test 'proved' reattach by remembering it in a Python variable.
HP-1466-01: files kept forever with no way to see or remove them is not a
policy, it is accumulation.

New: houseplan/plans/list (name, url, size, modified, and which spaces use it)
and houseplan/plans/delete, which refuses while a space still references the
file — the stored configuration answers that, not the client. In the space
dialog, 'Already uploaded' shows the list with thumbnails; one click attaches,
reading the aspect from the image as an upload does; the trash button is the
only way a plan file is ever deleted.

That also bounds the disk without any timer, which is the part every automatic
attempt got wrong: v1.46.4 deleted detached plans, v1.46.5 raced the retry that
was about to reference an upload. The user decides, and can now see what they
are deciding about.

Docs: comments in plans.py and websocket_api.py still described the age-based
collection v1.46.6 removed (report §6); ARCHITECTURE gained the two new routes
and an explanation of why the listing is what makes 'never delete' livable.

demo/smoke_saved_plans.mjs

@@ -0,0 +1,85 @@
+// «Уже загруженные»: план, который не удаляется за ненадобностью, обязан быть
+// находимым. Иначе обещание «отцепил — файл остался» неполноценно: вернуть его
+// из карточки было нельзя, старый URL нигде не хранится (HP-1466-02).
+// Заодно это единственный способ удалить план — явным действием.
+import { launch, checkAll, finish } from './serve.mjs';
+const { page, browser } = await launch({ width: 900, height: 1000 }, 1);
+const res = await page.evaluate(async () => {
+  const out = {};
+  const c = window.__card;
+  const sr = () => c.shadowRoot || c.renderRoot;
+  const base = c.hass.callWS;
+
+  let serverPlans = [
+    { name: 'f1.aaa.png', url: '/api/houseplan/content/plans/_/f1.aaa.png', size: 121335, modified: 2, used_by: [] },
+    { name: 'f2.bbb.png', url: '/api/houseplan/content/plans/_/f2.bbb.png', size: 26931, modified: 1, used_by: ['2 этаж'] },
+  ];
+  const deleted = [];
+  c.hass = { ...c.hass, callWS: async (m) => {
+    if (m.type === 'houseplan/plans/list') return { plans: serverPlans };
+    if (m.type === 'houseplan/plans/delete') {
+      const p = serverPlans.find((x) => x.name === m.name);
+      if (p?.used_by.length) { const e = new Error('in_use'); e.code = 'in_use'; throw e; }
+      deleted.push(m.name);
+      serverPlans = serverPlans.filter((x) => x.name !== m.name);
+      return { ok: true, removed: true };
+    }
+    if (m.type === 'houseplan/content/sign') {
+      const urls = {}; for (const p of m.paths) urls[p] = p + '?authSig=X'; return { urls };
+    }
+    return base(m);
+  } };
+  window.confirm = () => true;
+
+  // пространство без плана — как после отцепления
+  c._openSpaceDialog('edit', 'f1'); await c.updateComplete;
+  c._spaceDialog = { ...c._spaceDialog, source: 'file', planUrl: null, planFile: null };
+  await c.updateComplete;
+  out.saveBlockedWithoutPlan = !!sr().querySelector('.dialog .btn.on[disabled]');
+
+  // открываем список сохранённых
+  await c._toggleServerPlans();
+  await new Promise((r) => setTimeout(r, 60));
+  await c.updateComplete;
+  const rows = [...sr().querySelectorAll('.savedplan')];
+  out.listed = rows.length;
+  out.showsUsage = (rows[1]?.textContent || '').includes('2 этаж');
+  out.deleteDisabledForUsed = !!rows[1]?.querySelector('.btn.danger[disabled]');
+  out.deleteEnabledForFree = !rows[0]?.querySelector('.btn.danger[disabled]');
+  out.thumbnailSigned = (rows[0]?.querySelector('img')?.getAttribute('src') || '').includes('authSig=');
+
+  // выбираем свободный план — он подставляется в диалог
+  c._useServerPlan(serverPlans[0].url);
+  await new Promise((r) => setTimeout(r, 80));
+  await c.updateComplete;
+  out.picked = c._spaceDialog.planUrl === '/api/houseplan/content/plans/_/f1.aaa.png';
+  out.listClosed = !c._spaceDialog.pickSaved;
+  out.saveEnabledAfterPick = !sr().querySelector('.dialog .btn.on[disabled]');
+
+  // удаление: занятый нельзя, свободный можно
+  await c._toggleServerPlans();
+  await new Promise((r) => setTimeout(r, 60));
+  await c._deleteServerPlan('f2.bbb.png').catch(() => {});
+  out.usedNotDeleted = !deleted.includes('f2.bbb.png');
+  await c._deleteServerPlan('f1.aaa.png');
+  await c.updateComplete;
+  out.freeDeleted = deleted.includes('f1.aaa.png');
+  out.rowGone = !(c._spaceDialog.saved || []).some((p) => p.name === 'f1.aaa.png');
+  return out;
+});
+// зафиксировано прогоном на v1.47.0 и сверено с кодом
+checkAll(res, {
+  saveBlockedWithoutPlan: true,
+  listed: 2,
+  showsUsage: true,
+  deleteDisabledForUsed: true,
+  deleteEnabledForFree: true,
+  thumbnailSigned: true,
+  picked: true,
+  listClosed: true,
+  saveEnabledAfterPick: true,
+  usedNotDeleted: true,
+  freeDeleted: true,
+  rowGone: true,
+});
+await finish(browser);