fix: resolve SvelteKit route conflict by moving vote endpoint to /api/comment/[id]/vote

/api/comments/[id] and /api/comments/[slug] were ambiguous dynamic segments at
the same path level, causing a build error. Moved the vote handler to the
singular /api/comment/ prefix and updated all callers (web + iOS).

ios/LibNovel/LibNovel/Networking/APIClient.swift

@@ -342,7 +342,7 @@ actor APIClient {
     /// Cast, change, or toggle-off a vote on a comment.
     /// Returns the updated BookComment (with refreshed upvotes/downvotes counts).
     func voteComment(commentId: String, vote: String) async throws -> BookComment {
-        try await fetch("/api/comments/\(commentId)/vote", method: "POST", body: VoteBody(vote: vote))
+        try await fetch("/api/comment/\(commentId)/vote", method: "POST", body: VoteBody(vote: vote))
     }
 
     /// Delete a comment (and its replies) by ID. Only the owner can delete.