feat(scribe): snippet management UI + REST routes; embed snippets on create

Step 6 of the Drafter recall milestone (#227): a human-facing surface for
the reusable-code snippets that agents record via MCP, plus the REST API
behind it. Backend embeds snippets inline on create/update so they're
recallable immediately, not only after a restart.

Backend:
- routes/snippets.py: GET/POST /api/snippets, GET/PATCH/DELETE
  /api/snippets/<id>. Share-aware per rule #78 (get_note_for_user +
  can_write_note), writes performed as the owner; list owner-scoped —
  mirrors routes/notes.py. Registered in app.py.
- services/snippets.py: embed on create/update via a _embed_snippet
  fire-and-forget helper, covering BOTH the MCP tool and the REST route
  by construction. A snippet's value is immediate recall, so it can't wait
  for the startup-only backfill (see issue: MCP create path doesn't embed
  inline for notes/tasks generally).
- tests/test_routes_snippets.py: structural registration + handler/service
  contract + PATCH-field ↔ update_snippet-kwarg parity (rule #33).

Frontend (Vue 3 + TS):
- api/snippets.ts: typed client, modeled on api/systems.ts.
- views: SnippetListView (search, skeleton/empty/error states),
  SnippetDetailView (read + copy-to-clipboard, ConfirmDialog delete),
  SnippetEditorView (create/edit all fields, Ctrl/Cmd+S, Esc, autofocus,
  validation). v1 quality per rules #24/#27.
- router: /snippets, /snippets/new, /snippets/:id, /snippets/:id/edit.
- NoteType union widened to include 'snippet'; Snippets nav link added to
  AppHeader (desktop pill bar + mobile menu).
- Design system: Moss --color-action-primary for action buttons, accent
  --color-primary reserved for tags/brand (Hybrid rule); focus rings;
  JetBrains Mono for code/name/signature/location.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Pa2EsuB54BuWQ8GfJq9c7t

src/scribe/app.py

@@ -29,6 +29,7 @@ from scribe.routes.plugin import plugin_bp
 from scribe.routes.trash import trash_bp
 from scribe.routes.dashboard import dashboard_bp
 from scribe.routes.systems import systems_bp
+from scribe.routes.snippets import snippets_bp
 from scribe.mcp import mount_mcp
 
 STATIC_DIR = Path(__file__).parent / "static"
@@ -91,6 +92,7 @@ def create_app() -> Quart:
     app.register_blueprint(trash_bp)
     app.register_blueprint(dashboard_bp)
     app.register_blueprint(systems_bp)
+    app.register_blueprint(snippets_bp)
 
     @app.before_request
     async def before_request():