unify terms to 'spreads'

This commit only renames things, changes no logic.  Any mention of "book", "view", or "mode" is renamed in relation to "spreads".

The AnchoredBox.jsx file is renamed to Anchored.jsx

Extra icons are deleted, and the remaining ones are renamed.

client/components/Anchored.less

@@ -0,0 +1,58 @@
+.anchored-trigger {
+	&.active {
+		background-color: #444444;
+	}
+}
+
+.anchored-box {
+	position:absolute;
+	top: 30px;
+	@supports (inset-block-start: anchor(bottom)){
+		inset-block-start: anchor(bottom);
+	}
+	justify-self: anchor-center;
+	visibility: hidden;
+	&.active {
+		visibility: visible;
+	}
+	padding          : 15px;
+	color            : white;
+	background-color : #555555;
+	border-radius    : 5px;
+	font-size        : .8em;
+	margin-top       : 10px;
+
+	h1 {
+		border-bottom: 1px solid currentColor;
+		margin-bottom: 0.5em;
+		padding-bottom: 0.3em;
+	}
+
+	h2 {
+		color: lightgray;
+		border-bottom: 1px solid currentColor;
+		margin: 1em 0 0.5em 0;
+		padding-bottom: 0.3em;
+	}
+
+	label {
+		display: flex;
+		align-items: center;
+		justify-content: space-between;
+		gap: 6px;
+
+	}
+
+	&:before {
+		content: "";
+		width: 0px;
+		height: 0px;
+		position: absolute;
+		border: 10px solid transparent;
+		border-bottom: 10px solid #555555;
+		left: 50%;
+		transform: translateX(-50%);
+		top: -20px;
+		pointer-events: none;
+	  }
+}