enhance illustration being taken into account in the response

backend/src/main/java/com/aiteacher/chat/ChatService.java

@@ -29,7 +29,7 @@ public class ChatService {
         - Use clear structure: headings, bullet points, or numbered steps where appropriate to maximize clarity
         - Only say you cannot answer if the context is entirely unrelated to the question
         - Cite sources for each major claim using the reference labels from the context (e.g. [S1], [F2]). Prefer these labels over inventing page numbers, but you may also describe the source naturally if needed.
-        - When referencing diagrams or figures, prefer their label from the context (e.g. [F1])
+        - Figures (labeled [F1], [F2], etc.) are actual images and drawings from the textbook — they will be rendered as inline illustrations in your response. Use them actively to support your explanations: reference a figure when it visually demonstrates anatomy, a surgical step, or a clinical concept you are describing.
         - Maintain continuity with the conversation history
         - Never fabricate clinical information not present in the context
         """;

backend/src/main/java/com/aiteacher/topic/TopicSummaryResponse.java

@@ -14,9 +14,15 @@ public record TopicSummaryResponse(
     Instant generatedAt
 ) {
     public record SourceReference(
+        String type,
+        String refLabel,
         String bookId,
         String bookTitle,
-        Integer page
+        Integer page,
+        String figureId,
+        String label,
+        String caption,
+        String imageUrl
     ) {
     }
 }

backend/src/main/java/com/aiteacher/topic/TopicSummaryService.java

@@ -35,6 +35,7 @@ public class TopicSummaryService {
         - Structure your response clearly with key points
         - Cite claims using ONLY the reference labels provided in the context (e.g. [S1], [F2]).
           Do not invent page numbers, section titles, or labels not present in the CONTEXT block.
+        - Figures (labeled [F1], [F2], etc.) are actual images and drawings from the textbook — they will be rendered as inline illustrations in your response. Use them actively to support your explanations: reference a figure when it visually demonstrates anatomy, a surgical step, or a clinical concept you are describing.
         - If the retrieved context does not contain sufficient information on the topic,
           explicitly state: "The uploaded books do not contain sufficient information on this topic."
         - Never hallucinate or fabricate clinical information
@@ -135,7 +136,7 @@ public class TopicSummaryService {
         return String.format(
             "Provide a comprehensive educational summary of the following neurosurgery topic: " +
             "%s. Topic description: %s. " +
-            "Include key concepts, clinical considerations, and important details that a neurosurgeon should know.",
+            "Include key concepts, diagrams, illustations and clinical considerations, and important details that a neurosurgeon should know.",
             topic.getName(), topic.getDescription()
         );
     }
@@ -165,7 +166,7 @@ public class TopicSummaryService {
                   .append(f.getCaption() != null ? f.getCaption() : "")
                   .append("\n");
             }
-            sb.append("\n");
+            sb.append("\nWhen referencing diagrams, use their label from the context (e.g. [F1]).\n\n");
         }
 
         sb.append("QUESTION:\n").append(question);
@@ -177,27 +178,35 @@ public class TopicSummaryService {
                                                                       List<Book> readyBooks) {
         List<TopicSummaryResponse.SourceReference> sources = new ArrayList<>();
 
-        for (SectionEntity s : sections) {
+        for (int i = 0; i < sections.size(); i++) {
+            SectionEntity s = sections.get(i);
             Book book = readyBooks.stream()
                 .filter(b -> b.getId().equals(s.getBookId()))
                 .findFirst()
                 .orElse(null);
             String title = book != null ? book.getTitle() : "Book";
             String bookId = book != null ? book.getId().toString() : null;
-            sources.add(new TopicSummaryResponse.SourceReference(bookId, title, s.getPageStart()));
+            sources.add(new TopicSummaryResponse.SourceReference(
+                "TEXT", "S" + (i + 1), bookId, title, s.getPageStart(),
+                null, null, null, null));
         }
 
-        for (FigureEntity f : figures) {
+        for (int i = 0; i < figures.size(); i++) {
+            FigureEntity f = figures.get(i);
             Book book = readyBooks.stream()
                 .filter(b -> b.getId().equals(f.getBookId()))
                 .findFirst()
                 .orElse(null);
             String title = book != null ? book.getTitle() : "Book";
             String bookId = book != null ? book.getId().toString() : null;
-            sources.add(new TopicSummaryResponse.SourceReference(bookId, title, f.getPage()));
+            String filename = f.getImagePath().substring(f.getImagePath().lastIndexOf('/') + 1);
+            String imageUrl = "/api/v1/figures/" + f.getBookId() + "/" + filename;
+            sources.add(new TopicSummaryResponse.SourceReference(
+                "FIGURE", "F" + (i + 1), bookId, title, f.getPage(),
+                f.getId(), f.getLabel(), f.getCaption(), imageUrl));
         }
 
-        return sources.stream().distinct().toList();
+        return sources;
     }
 
     private String serializeSources(List<TopicSummaryResponse.SourceReference> sources) {