[Bug]: Client crash after many "Sqlite prepare statement error: "database is locked""

### ⚠️ Before submitting, please verify the following: ⚠️

- [x] This is a **bug**, not a question or a configuration issue.
- [x] This issue is **not** already reported on Github (I've searched it).
- [x] Nextcloud Server and Desktop Client are **up to date**. See [Server Maintenance and Release Schedule](https://github.com/nextcloud/server/wiki/Maintenance-and-Release-Schedule) and [Desktop Releases](https://nextcloud.com/install/#install-clients) for supported versions.
- [x] I agree to follow Nextcloud's [Code of Conduct](https://nextcloud.com/contribute/code-of-conduct/)

### Bug description

Since some time (can't remember when), the NC desktop client regularly display sync error then crash and restart after a moment.
I have many different folders synced from two servers, with lot of excludes that is re-synced after restart.

In the log :
```
2025-12-01 02:23:46:230 [ warning nextcloud.sync.database.sql ./src/common/ownsql.cpp:253 ]: Sqlite prepare statement error: "database is locked" in "PRAGMA quick_check;"
2025-12-01 02:23:46:230 [ warning nextcloud.sync.database.sql ./src/common/ownsql.cpp:85 ]: Error preparing quick_check on database
2025-12-01 02:23:46:230 [ critical nextcloud.sync.database.sql ./src/common/ownsql.cpp:138 ]: Consistency check failed, removing broken db "/media/wargreen/Cagette/KompleX KapharnauM/.sync_04e5b023b31e.db"
2025-12-01 02:23:46:245 [ info nextcloud.sync.database ./src/common/syncjournaldb.cpp:335 ]: sqlite3 version "3.46.1"
2025-12-01 02:23:46:245 [ info nextcloud.sync.database ./src/common/syncjournaldb.cpp:347 ]: sqlite3 locking_mode= "exclusive"
2025-12-01 02:23:46:245 [ info nextcloud.sync.database ./src/common/syncjournaldb.cpp:355 ]: sqlite3 journal_mode= "wal"
2025-12-01 02:23:46:337 [ info nextcloud.sync.database ./src/common/syncjournaldb.cpp:377 ]: sqlite3 synchronous= "NORMAL"
2025-12-01 02:23:46:382 [ info nextcloud.sync.database ./src/common/syncjournaldb.cpp:2491 ]: Forcing remote re-discovery by deleting folder Etags
2025-12-01 02:23:46:382 [ info nextcloud.gui.folder.manager ./src/gui/folderman.cpp:1306 ]: Adding folder to Folder Map OCC::Folder(0x563cd840b1d0) "14"
2025-12-01 02:23:46:451 [ info nextcloud.gui.folder.manager ./src/gui/folderman.cpp:737 ]: Schedule folder "14" to sync!
2025-12-01 02:23:46:451 [ info nextcloud.gui.folder.manager ./src/gui/folderman.cpp:750 ]: Folder is not ready to sync, not scheduled!
2025-12-01 02:23:46:451 [ info nextcloud.sync.configfile ./src/libsync/configfile.cpp:1302 ]: Adding user defined ignore list to csync: "/home/wargreen/.config/Nextcloud/sync-exclude.lst"
2025-12-01 02:25:28:638 [ warning nextcloud.sync.database.sql ./src/common/ownsql.cpp:253 ]: Sqlite prepare statement error: "database is locked" in "PRAGMA quick_check;"
2025-12-01 02:25:28:638 [ warning nextcloud.sync.database.sql ./src/common/ownsql.cpp:85 ]: Error preparing quick_check on database
2025-12-01 02:25:28:638 [ critical nextcloud.sync.database.sql ./src/common/ownsql.cpp:138 ]: Consistency check failed, removing broken db "/media/wargreen/***redacted***/.sync_d84ece4ec6f4.db"
2025-12-01 02:25:28:644 [ info nextcloud.sync.database ./src/common/syncjournaldb.cpp:335 ]: sqlite3 version "3.46.1"
2025-12-01 02:25:28:644 [ info nextcloud.sync.database ./src/common/syncjournaldb.cpp:347 ]: sqlite3 locking_mode= "exclusive"
2025-12-01 02:25:28:644 [ info nextcloud.sync.database ./src/common/syncjournaldb.cpp:355 ]: sqlite3 journal_mode= "wal"
2025-12-01 02:25:28:724 [ info nextcloud.sync.database ./src/common/syncjournaldb.cpp:377 ]: sqlite3 synchronous= "NORMAL"
2025-12-01 02:25:28:740 [ info nextcloud.sync.database ./src/common/syncjournaldb.cpp:2491 ]: Forcing remote re-discovery by deleting folder Etags
2025-12-01 02:25:28:740 [ info nextcloud.gui.folder.manager ./src/gui/folderman.cpp:1306 ]: Adding folder to Folder Map OCC::Folder(0x563cd8452980) "2"
2025-12-01 02:25:28:762 [ info nextcloud.gui.folder.manager ./src/gui/folderman.cpp:737 ]: Schedule folder "2" to sync!
2025-12-01 02:25:28:762 [ info nextcloud.gui.folder.manager ./src/gui/folderman.cpp:750 ]: Folder is not ready to sync, not scheduled!
2025-12-01 02:25:28:762 [ info nextcloud.sync.configfile ./src/libsync/configfile.cpp:1302 ]: Adding user defined ignore list to csync: "/home/wargreen/.config/Nextcloud/sync-exclude.lst"
2025-12-01 02:27:10:944 [ warning nextcloud.sync.database.sql ./src/common/ownsql.cpp:253 ]: Sqlite prepare statement error: "database is locked" in "PRAGMA quick_check;"
2025-12-01 02:27:10:944 [ warning nextcloud.sync.database.sql ./src/common/ownsql.cpp:85 ]: Error preparing quick_check on database
2025-12-01 02:27:10:944 [ critical nextcloud.sync.database.sql ./src/common/ownsql.cpp:138 ]: Consistency check failed, removing broken db "/media/wargreen/***redacted***Synchro/.sync_baeee5e0f979.db"
```

The log folder seem to be full of new logs :
```
....
20251201_0248_nextcloud.log.2.gz
20251201_0248_nextcloud.log.3.gz
20251201_0248_nextcloud.log.4.gz
20251201_0248_nextcloud.log.5.gz
20251201_0248_nextcloud.log.6.gz
20251201_0248_nextcloud.log.7.gz
20251201_0248_nextcloud.log.8.gz
20251201_0248_nextcloud.log.9.gz
20251201_0248_permanent_delete.log.0
20251201_0249_nextcloud.log.0.gz
20251201_0249_nextcloud.log.10
20251201_0249_nextcloud.log.11
20251201_0249_nextcloud.log.1.gz
20251201_0249_nextcloud.log.2.gz
20251201_0249_nextcloud.log.3.gz
20251201_0249_nextcloud.log.4.gz
20251201_0249_nextcloud.log.5.gz
20251201_0249_nextcloud.log.6.gz
20251201_0249_nextcloud.log.7.gz
20251201_0249_nextcloud.log.8.gz
20251201_0249_nextcloud.log.9.gz
```

The last lines before a crash-and-restart :
```
2025-12-01 02:49:23:319 [ info nextcloud.sync.engine ./src/libsync/syncengine.cpp:921 ]: Sync run took 71824 ms
2025-12-01 02:49:23:320 [ info nextcloud.gui.folder ./src/gui/folder.cpp:1266 ]: Client version 4.0.1-2 (Debian built) Qt 6.9.2 SSL OpenSSL 3.5.4 30 Sep 2025
2025-12-01 02:49:23:320 [ info nextcloud.gui.folder ./src/gui/folder.cpp:1275 ]: SyncEngine finished without problem.
2025-12-01 02:49:23:320 [ info nextcloud.gui.folder ./src/gui/folder.cpp:436 ]: Folder "" sync result: OCC::SyncResult::NotYetStarted
2025-12-01 02:49:23:320 [ info nextcloud.gui.application ./src/gui/owncloudgui.cpp:244 ]: Sync state changed for folder "https://cloud.latendresse.fr/remote.php/dav/files/wargreen/" : "Success, some files were ignored."
```

### Steps to reproduce

Not sure.

### Expected behavior

Don't crash, reliable sync

### Which files are affected by this bug

CE_VALKA_OK.wav, IMG_1275 (1).jpg

### Operating system

Linux

### Which version of the operating system you are running.

Debian SID

### Package

Distro package manager

### Nextcloud Server version

31.0.10

### Nextcloud Desktop Client version

4.0.1-2

### Is this bug present after an update or on a fresh install?

Updated from a minor version (ex. 3.16.1 to 3.16.2)

### Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

### Are you using an external user-backend?

- [x] Default internal user-backend
- [ ] LDAP/ Active Directory
- [ ] SSO - SAML
- [ ] Other

### Nextcloud Server logs

```shell
None related.
```

### Additional info

Can send a debug archive in a private way.

### Update

I have managed to get it working, by disabling the sync of a directory that contain few git repos with few thousands of files.
Enabling these dir one by one make all the dirs gone synced and all seem work well now.