Update BookProgress model and schemas

Updated book progress model in anticipation of the KOReader sync
feature.

Renamed properties:
 - renamed "progress" to "percentage"
 - renamed "pdf_loc" to "pdf_page"
 - renamed "epub_loc" to "epub_cfi"

New properties:
 - "epub_xpointer", marks the location of an epub in KOReader
 - "device", the device type that updated the progress
 - "device_id", the id of the device that updated the progress

frontend/src/lib/components/reader/epub-reader.svelte

@@ -79,8 +79,8 @@
 			await fetch(`/api/books/progress/${bookId}`, {
 				method: 'POST',
 				body: JSON.stringify({
-					progress: currentProgress,
-					epub_loc: currentLocation,
+					percentage: currentProgress,
+					epub_cfi: currentLocation,
 					completed: currentProgress === 1
 				})
 			});

frontend/src/lib/components/view/book-thumbnail.svelte

@@ -38,9 +38,9 @@
 				: ''}"
 		/>
 	</a>
-	{#if book.progress?.progress && !selected && !darkened}
+	{#if book.progress?.percentage && !selected && !darkened}
 		<Progress
-			value={book.progress.progress}
+			value={book.progress.percentage}
 			max={1}
 			class="mt-[-8px] h-1 rounded {book.progress.completed
 				? '[&>div]:bg-green-600'

frontend/src/routes/(root)/(library)/book/[bookId]/+page.svelte

@@ -68,9 +68,9 @@
 					class="h-full w-full overflow-hidden rounded object-cover"
 				/>
 
-				{#if book?.progress?.progress}
+				{#if book?.progress?.percentage}
 					<Progress
-						value={book?.progress.progress}
+						value={book?.progress.percentage}
 						max={1}
 						color={book?.progress.completed ? 'bg-green-600' : 'bg-yellow-500'}
 						class="mt-[-8px] h-2 rounded {book?.progress.completed