doc: update database diagram

Signed-off-by: Richard Zak <richard.j.zak@gmail.com>

Author: rjzak

crates/server/src/db/readme.md

@@ -123,4 +123,15 @@ erDiagram
         int lid PK
         timestamp added
     }
+    PAGINATION {
+        uuid id PK
+        int userid FK
+        int next_fileid FK
+        string query
+        string query_type "Enum options: search, similaritysearch"
+        int total_results
+        timestamp created
+    }
+    PAGINATION ||--}| PERSON : has
+    PAGINATION ||--|| FILE : has
 ```