feat(gamification): Phase 1 — full kill-switch + textbook XP wrapping

Until now the 'gamification' feature flag did nothing: it had no row in
app_settings, the admin couldn't toggle it, awardXP/awardCoins ignored
it, and the CSS only hid three dashboard widgets — XP bars in textbooks
stayed visible regardless.

Phase 1 closes every hole.

Backend (source of truth):
  • migration 029 seeds feature_gamification_enabled=1
  • new isGamificationEnabled() helper in gamification/_shared.js with a
    30s cache + invalidateGamificationCache() for instant admin toggles
  • awardXP / awardCoins / updateStreak / unlockAchievement /
    checkAchievements all bail out when the flag is off
  • /api/gamification/* and /api/shop/* (user routes) return 404 when
    disabled; admin routes remain open so the switch itself is reachable
  • adminController.updateFeatures gains 'gamification' in the allow-list
    and invalidates the cache on flip

Frontend:
  • LS.isGamificationEnabled() (synchronous, populated by loadFeatures)
    so xp.js + applyCosmetics can bail without a round-trip
  • xp.js load/add/flush become no-ops when the flag is off
  • applyCosmetics skips the round-trip when off
  • CSS .no-gamification rule expanded to cover .hero-xp-badge, .po-xp,
    .xp-card, .xp-bar, #frames-section, and a universal [data-gamified]
    hook for future blocks

Textbooks (Variant 2 of the plan):
  • backend/scripts/wrap_textbook_xp.py — idempotent script that adds
    data-gamified to 167 XP tags across 63 textbook files (chapters +
    hubs, all subjects/grades). Single CSS rule now hides everything.

Verified end-to-end: with the flag off, awardXP/awardCoins write nothing;
flipping back restores normal behavior.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/scripts/wrap_textbook_xp.py

@@ -0,0 +1,90 @@
+#!/usr/bin/env python3
+"""
+wrap_textbook_xp.py — Add `data-gamified` attribute to XP UI in textbooks.
+
+Part of Phase 1 of the gamification kill-switch (Variant 2 of plan §E.3).
+The CSS rule `body.no-gamification [data-gamified] { display:none }`
+catches every wrapped block in one selector, so future authors don't have
+to invent new class names just to be hidden by the master switch.
+
+What we wrap:
+  • <div id="hero-xp-badge" ...>           — chapter & hub hero badges
+  • <div class="po-xp" ...>                 — hub overall-progress XP pill
+  • <div class="xp-card" ...>               — chapter inline progress card
+  • inline JS that generates `<div class="xp-card">` HTML strings
+  • `.xp-bar` containers when they're standalone
+
+Idempotent: if `data-gamified` is already present on an opening tag the
+script skips it. Reports each file touched.
+
+Run from repo root:
+    python backend/scripts/wrap_textbook_xp.py
+"""
+import re
+import sys
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[2] / "frontend" / "textbooks"
+if not ROOT.is_dir():
+    print(f"[wrap-xp] textbook dir not found: {ROOT}", file=sys.stderr)
+    sys.exit(1)
+
+# Selectors that mark an opening tag as an XP block. The first group
+# captures `<tag` + attributes UP TO (but not including) the existing
+# `class="..."` / `id="..."` we matched, so we can splice in
+# `data-gamified` before the closing `>`.
+PATTERNS = [
+    # <... id="hero-xp-badge" ...>
+    re.compile(r'(<[a-zA-Z][^>]*?\bid="hero-xp-badge"[^>]*?)(>)'),
+    # <... class="po-xp" ...> or class="...po-xp..."
+    re.compile(r'(<[a-zA-Z][^>]*?\bclass="[^"]*\bpo-xp\b[^"]*"[^>]*?)(>)'),
+    # <... class="...xp-card..."> — covers HTML and inline JS `'<div class="xp-card">'`
+    re.compile(r'(<[a-zA-Z][^>]*?\bclass="[^"]*\bxp-card\b[^"]*"[^>]*?)(>)'),
+    # Standalone class="hero-xp-badge"
+    re.compile(r'(<[a-zA-Z][^>]*?\bclass="[^"]*\bhero-xp-badge\b[^"]*"[^>]*?)(>)'),
+]
+
+# Already-wrapped check
+RX_HAS_ATTR = re.compile(r'\bdata-gamified\b')
+
+
+def patch_file(path: Path) -> int:
+    """Return number of opening tags newly given data-gamified."""
+    text = path.read_text(encoding="utf-8")
+    new = text
+    changes = 0
+    for rx in PATTERNS:
+        def sub(m, _rx=rx):
+            nonlocal changes
+            head, close = m.group(1), m.group(2)
+            if RX_HAS_ATTR.search(head):
+                return m.group(0)
+            changes += 1
+            sep = "" if head.endswith(" ") else " "
+            return f'{head}{sep}data-gamified{close}'
+        new = rx.sub(sub, new)
+    if new != text:
+        path.write_text(new, encoding="utf-8")
+    return changes
+
+
+def main():
+    files = sorted(ROOT.glob("*.html"))
+    total_files = 0
+    total_tags = 0
+    for f in files:
+        try:
+            n = patch_file(f)
+        except Exception as e:
+            print(f"[wrap-xp] {f.name}: ERROR {e}", file=sys.stderr)
+            continue
+        if n:
+            print(f"[wrap-xp] {f.name}: +{n} tag(s)")
+            total_files += 1
+            total_tags += n
+    print(f"[wrap-xp] done — patched {total_tags} tags across {total_files} files "
+          f"(scanned {len(files)})")
+
+
+if __name__ == "__main__":
+    main()