fix FT note→post renames in test_sharing & test_layout_and_styling; note page layout polish

- test_sharing.py: NotePage→PostPage, MyNotesPage→MyPostsPage, add_note_item→add_post_line,
  share_note_with→share_post_with, get_note_owner→get_post_owner; navigate to /billboard/
- test_layout_and_styling.py: NotePage→PostPage, get_item_input_box→get_line_input_box,
  add_note_item→add_post_line; navigate to /billboard/
- my_notes.html: remove "My Notes" h2 heading
- _note.scss: .note-page padding 0.75rem 1.5rem; .note-don-doff top:-1rem (DON centers on
  corner), gap:0.4rem (tight like game kit); .note-item padding-left:1.25rem (left buffer)

Code architected by Disco DeDisco <discodedisco@outlook.com>
Git commit message Co-Authored-By:
Claude Sonnet 4.6 <noreply@anthropic.com>

src/templates/apps/billboard/my_notes.html

@@ -6,7 +6,6 @@
 
 {% block content %}
 <div class="note-page">
-    <h2>My Notes</h2>
     <ul class="note-list">
         {% for item in note_items %}
         <li class="note-item" data-slug="{{ item.obj.slug }}"