note title equip: DON/DOFF buttons outside top-left corner; User.active_title FK; don/doff views; greeting updated via JS — TDD

- lyric/models.py: active_title = ForeignKey('drama.Note', null=True, SET_NULL)
- lyric migration 0020_add_active_title
- billboard/views.py: don_title + doff_title views; is_equipped per note_item context
- billboard/urls.py: note/<slug>/don + note/<slug>/doff routes
- _navbar.html: id_greeting_name span; shows active_title.slug|capfirst when set
- my_notes.html: .note-don-doff buttons (DON/DOFF, × when disabled); data-don-url/doff-url/title attrs
- note-page.js: _bindDonDoff() — DON POST sets greeting + swaps btn state; DOFF restores Earthman
- _note.scss: .note-don-doff position:absolute left:-1rem top:0; flex-direction:column gap:1.25rem
- ITs: NoteEquipTitleViewTest (5 tests); UserModelTest.test_active_title_* (3 tests)
- FT: NoteEquipTitleTest.test_don_equips_title_greeting_and_doff_restores

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

src/apps/lyric/models.py

@@ -44,6 +44,10 @@ class User(AbstractBaseUser):
     unlocked_decks = models.ManyToManyField(
         "epic.DeckVariant", blank=True, related_name="unlocked_by",
     )
+    active_title = models.ForeignKey(
+        "drama.Note", null=True, blank=True,
+        on_delete=models.SET_NULL, related_name="+",
+    )
     ap_public_key = models.TextField(blank=True, default="")
     ap_private_key = models.TextField(blank=True, default="")