fix(plugin): screenshot limit, version/build fields, delete button, workspace scripts

- list_screenshots: bump limit 12 → 50 so users can scroll further back
- Add versionString + buildId to DeckyVaultImportV1, SessionData, and
  buildImportPayload. Import endpoint now saves them on new game versions.
- Screenshot delete button in preset detail modal: owner/admin sees a
  trash icon on hover that calls DELETE /api/performance/:id/screenshots/:sid
- Root workspace scripts for plugin workflow:
  bun run plugin:build  | plugin:zip | plugin:release | plugin:deploy
- Add deploy.sh (SSH scripts to push plugin to Deck)

plugins/decky-vault/main.py

@@ -605,7 +605,7 @@ exec mangohud "$@"
         except Exception as e:
             return {"success": False, "error": str(e), "status": 0}
 
-    async def list_screenshots(self, limit: int = 12) -> dict:
+    async def list_screenshots(self, limit: int = 50) -> dict:
         """RPC: List recent Steam Deck screenshots from ~/Pictures/Screenshots/.
         Returns {screenshots: [{path, name, mtime, size}], error?}.
         Steam saves timestamped JPGs in a 'Steam Client' subfolder and keeps