Batch session inserts into single transaction

Replace per-item add_session with add_sessions using add_all.
No fallback on IntegrityError -- duplicate concurrent submissions
are the client's responsibility.

backend/endpoints/play_sessions.py

@@ -2,7 +2,6 @@ from datetime import datetime, timedelta, timezone
 
 from fastapi import HTTPException, Request, status
 from pydantic import BaseModel, Field, model_validator
-from sqlalchemy.exc import IntegrityError
 
 from decorators.auth import protected_route
 from endpoints.responses.play_session import (
@@ -121,6 +120,7 @@ def ingest_play_sessions(
     )
 
     seen_keys: set[tuple[str | None, int | None, datetime]] = set()
+    to_insert: list[tuple[int, int | None, PlaySession]] = []
 
     for (idx, resolved_rom_id), item in zip(resolved, payload.sessions, strict=False):
         if idx in skipped_indices:
@@ -138,40 +138,33 @@ def ingest_play_sessions(
             continue
         seen_keys.add(dedup_key)
 
-        play_session = PlaySession(
-            user_id=user_id,
-            device_id=resolved_device_id,
-            rom_id=resolved_rom_id,
-            save_slot=item.save_slot,
-            start_time=item.start_time,
-            end_time=item.end_time,
-            duration_ms=item.duration_ms,
+        to_insert.append(
+            (
+                idx,
+                resolved_rom_id,
+                PlaySession(
+                    user_id=user_id,
+                    device_id=resolved_device_id,
+                    rom_id=resolved_rom_id,
+                    save_slot=item.save_slot,
+                    start_time=item.start_time,
+                    end_time=item.end_time,
+                    duration_ms=item.duration_ms,
+                ),
+            )
         )
 
-        try:
-            created = db_play_session_handler.add_session(play_session)
+    if to_insert:
+        db_play_session_handler.add_sessions([ps for _, _, ps in to_insert])
+        for idx, resolved_rom_id, ps in to_insert:
             results.append(
-                PlaySessionIngestResult(
-                    index=idx,
-                    status="created",
-                    id=created.id,
-                )
+                PlaySessionIngestResult(index=idx, status="created", id=ps.id)
             )
             created_count += 1
-
             if resolved_rom_id is not None:
                 existing = rom_user_updates.get(resolved_rom_id)
-                if existing is None or item.end_time > existing:
-                    rom_user_updates[resolved_rom_id] = item.end_time
-
-        except IntegrityError:
-            results.append(
-                PlaySessionIngestResult(
-                    index=idx,
-                    status="duplicate",
-                )
-            )
-            skipped_count += 1
+                if existing is None or ps.end_time > existing:
+                    rom_user_updates[resolved_rom_id] = ps.end_time
 
     for rom_id, latest_end_time in rom_user_updates.items():
         rom_user = db_rom_handler.get_rom_user(rom_id=rom_id, user_id=user_id)

backend/handler/database/play_sessions_handler.py

@@ -12,14 +12,14 @@ from .base_handler import DBBaseHandler
 
 class DBPlaySessionsHandler(DBBaseHandler):
     @begin_session
-    def add_session(
+    def add_sessions(
         self,
-        play_session: PlaySession,
+        play_sessions: list[PlaySession],
         session: Session = None,  # type: ignore
-    ) -> PlaySession:
-        session.add(play_session)
+    ) -> list[PlaySession]:
+        session.add_all(play_sessions)
         session.flush()
-        return play_session
+        return play_sessions
 
     @begin_session
     def find_existing(