feat: vault-aligned server v1 + UX polish

Redesign the optional FastAPI companion around vault files (manifest /
PUT/GET/DELETE + OCR jobs) instead of legacy strokes_json notes. Wire a
client Server settings panel for health/login. Polish shell UX: l10n for
settings/home/board, sticky-board empty state, and a narrow-screen
diagnostics FAB.

Co-authored-by: Cursor <cursoragent@cursor.com>

server/badnote_server/config.py

@@ -68,6 +68,9 @@ class Settings:
     jwt_secret: str = _resolve_jwt_secret()
     jwt_expiry_hours: int = int(os.environ.get("BADNOTE_JWT_EXPIRY_HOURS", "720"))
     cors_origins: list[str] = _resolve_cors_origins()
+    # Per-user vault trees (notebook folders + sidecars), independent of legacy
+    # notes.strokes_json storage.
+    vault_path: str = os.environ.get("BADNOTE_VAULT_PATH", "./data/vaults")
 
 
 settings = Settings()