Redesign study Notes, Reflection questions and Community pages; v2.12.0

- Notes: two-pane reader with searchable lesson list and snippets, track chips, friendlier empty states
- Reflection questions: numbered question cards, answered progress bar, unsaved-changes status, sticky save bar, share-to-discussion only when discussion is open
- Community: compact header, lesson browser sidebar with post counts (select on mobile), guidelines card, card-style posts

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "siteforge",
-  "version": "2.11.2",
+  "version": "2.12.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "siteforge",
-      "version": "2.11.2",
+      "version": "2.12.0",
       "dependencies": {
         "@aws-sdk/client-s3": "^3.1135.0",
         "@dnd-kit/core": "^6.3.1",