feat: book commenting system with upvote/downvote + fix profile SSR crash

- Add book_comments and comment_votes PocketBase collections (pb-init.sh + pocketbase.go EnsureCollections)
- Web: CommentsSection.svelte with post form, vote buttons, lazy-loaded per-book
- API routes: GET/POST /api/comments/[slug], POST /api/comments/[id]/vote
- iOS: BookComment + CommentsResponse models, fetchComments/postComment/voteComment in APIClient, CommentsView + CommentsViewModel wired into BookDetailView
- Fix profile page SSR crash (ERR_MODULE_NOT_FOUND cropperjs): lazy-load AvatarCropModal via dynamic import guarded by browser, move URL.createObjectURL into onMount

scripts/pb-init.sh

@@ -203,4 +203,29 @@ ensure_field "progress" "audio_time" "number"
 ensure_field "user_settings" "user_id" "text"
 ensure_field "app_users" "avatar_url" "text"
 
+create_collection "book_comments" '{
+  "name": "book_comments",
+  "type": "base",
+  "fields": [
+    {"name": "slug",       "type": "text",   "required": true},
+    {"name": "user_id",    "type": "text"},
+    {"name": "username",   "type": "text"},
+    {"name": "body",       "type": "text",   "required": true},
+    {"name": "upvotes",    "type": "number"},
+    {"name": "downvotes",  "type": "number"},
+    {"name": "created",    "type": "date"}
+  ]
+}'
+
+create_collection "comment_votes" '{
+  "name": "comment_votes",
+  "type": "base",
+  "fields": [
+    {"name": "comment_id", "type": "text", "required": true},
+    {"name": "user_id",    "type": "text"},
+    {"name": "session_id", "type": "text", "required": true},
+    {"name": "vote",       "type": "text", "required": true}
+  ]
+}'
+
 log "all collections ready"