feat: add mod editing, revision merges and secure game storage

Add immutable revisions, PGVN editor, asset replacement, merge and rebase workflows, authenticated media delivery and reachability GC. Harden the script interpreter, pin unrpyc and remove tracked build metadata. Include current compatibility checks, Naninovel import and regression tests.

backend/app/worker.py

@@ -10,6 +10,7 @@ from sqlalchemy import select, update
 from app.blobs import read_bytes
 from app.config import get_settings
 from app.converter.pipeline import convert_archive
+from app.converter.compatibility import CompatibilityError
 from app.db import SessionLocal
 from app.models import Game, GameVersion
 from app.routers.games import make_cover
@@ -36,7 +37,7 @@ async def claim() -> GameVersion | None:
             return None
         v = await db.get(GameVersion, version_id)
         v.status = "converting"
-        v.progress = "Начало конвертации"
+        v.progress = "Проверка совместимости игры"
         await db.commit()
         return v
 
@@ -48,6 +49,18 @@ async def process(v: GameVersion) -> None:
 
 
 async def convert(version_id: int, source: Path, filename: str) -> bool:
+    from app.maintenance import storage_access
+    async with storage_access():
+        task = asyncio.create_task(_convert(version_id, source, filename))
+        try:
+            return await asyncio.shield(task)
+        except asyncio.CancelledError:
+            # Conversion threads cannot be cancelled. Keep the lease until commit.
+            await task
+            raise
+
+
+async def _convert(version_id: int, source: Path, filename: str) -> bool:
     """Run the converter for a version and store the outcome. Returns success."""
     loop = asyncio.get_running_loop()
     work = get_settings().work_dir / str(version_id)
@@ -65,7 +78,7 @@ async def convert(version_id: int, source: Path, filename: str) -> bool:
             if version:
                 version.status = "failed"
                 version.progress = f"Ошибка: {e}"[:255]
-                version.report = {"error": str(e)}
+                version.report = e.report() if isinstance(e, CompatibilityError) else {"error": str(e)}
                 await db.commit()
         return False
     finally:
@@ -81,6 +94,8 @@ async def convert(version_id: int, source: Path, filename: str) -> bool:
         version.report = result.report
         version.size_bytes = result.size
         game = await db.get(Game, version.game_id)
+        if game:
+            game.engine = result.report.get("engine", "renpy")
         if game and not game.cover_hash and result.cover_source:
             try:
                 game.cover_hash = await asyncio.to_thread(make_cover,