feat!: remove the shared demo account

The demo account — one shared user that whitelisted emails entered from
the login page, reset on a schedule — goes end to end (owner decision,
E34): demo.py and the reset job, users.is_demo and demo_whitelist
(migration 0098 deletes the demo user, its audit rows, the reset job's
override and notices, then drops the column and table; the downgrade
restores the empty schema), the /auth/demo entry, the admin whitelist and
reset, the Demo tab, the banner, the login page's "Try the demo", and
every is_demo branch in routes, userscope, scheduler and the UI.

require_human only ever refused the demo account, so its 87 uses become
current_user (owner-approved); require_write_scope keeps its own check.
The login page's "or" divider now shows only beside the Google button:
without the demo entry under it, an instance without Google would have
said "or" to nothing.

A contract test (removedFeatures) fails on the word anywhere in the
backend, frontend, e2e or scripts — seen red on a planted hit. Size
ceilings tightened for the modules that shrank; admin.py is back under
the limit.

frontend/src/components/AppCommandPalette.tsx

@@ -151,34 +151,31 @@ export default function AppCommandPalette() {
           icon: <Keyboard className="w-4 h-4" />,
           run: toggleKeyboardHelp,
         },
-        // The debug recorder (E16) — not for the shared demo account, which cannot record. While
-        // it runs, Stop and a step marker take Start's place: the palette is reachable inside a
+        // The debug recorder (E16). While it runs, Stop and a step marker take Start's place: the palette is reachable inside a
         // player or a dialog where the pill's buttons are a long Tab away.
-        ...(me?.is_demo
-          ? []
-          : recordingSession
-            ? [
-                {
-                  id: "action:recorder:step",
-                  label: t("recorder.palette.step"),
-                  icon: <Flag className="w-4 h-4" />,
-                  run: () => markStep(""),
-                },
-                {
-                  id: "action:recorder:stop",
-                  label: t("recorder.palette.stop"),
-                  icon: <Square className="w-4 h-4" />,
-                  run: () => stopMutate(recordingSession.id),
-                },
-              ]
-            : [
-                {
-                  id: "action:recorder:start",
-                  label: t("recorder.palette.start"),
-                  icon: <Bug className="w-4 h-4" />,
-                  run: openRecorderStart,
-                },
-              ]),
+        ...(recordingSession
+          ? [
+              {
+                id: "action:recorder:step",
+                label: t("recorder.palette.step"),
+                icon: <Flag className="w-4 h-4" />,
+                run: () => markStep(""),
+              },
+              {
+                id: "action:recorder:stop",
+                label: t("recorder.palette.stop"),
+                icon: <Square className="w-4 h-4" />,
+                run: () => stopMutate(recordingSession.id),
+              },
+            ]
+          : [
+              {
+                id: "action:recorder:start",
+                label: t("recorder.palette.start"),
+                icon: <Bug className="w-4 h-4" />,
+                run: openRecorderStart,
+              },
+            ]),
         ...SCHEMES.map((s) => ({
           id: `action:theme:${s.id}`,
           label: t("palette.theme", { name: s.name }),