feat(history): report personal new-chapter count on read-progress list

Add `new_chapters_count` to each `GET /me/read-progress` item: how many
chapters sit past the reader's last-read chapter, computed by a correlated
subquery on chapter number. It is 0 when the reader is caught up, and 0
when the last-read chapter is unknown (manga-level progress or a deleted
chapter) so we never over-claim. (manga_id, number) is non-unique, so this
counts positions past the reader rather than distinct files.

Backs the personal "new since last read" indicator on the upcoming
Continue-reading shelf. Tests cover the mid-series, caught-up, and
no-read-chapter cases.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "mangalord-frontend",
-  "version": "0.94.1",
+  "version": "0.95.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "mangalord-frontend",
-      "version": "0.94.1",
+      "version": "0.95.0",
       "devDependencies": {
         "@lucide/svelte": "^1.16.0",
         "@playwright/test": "^1.48.0",

frontend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "mangalord-frontend",
-  "version": "0.94.1",
+  "version": "0.95.0",
   "private": true,
   "type": "module",
   "scripts": {