Handle large text files that would exhaust php memory_limit

[!NOTE]

• Currently exhausts PHP memory_limit
• Near term: Reject > X MB (e.g. memory_limit-128 or, safer, min(memory_limit-128, 100)
• Longer term: Implement streaming if deemed desirable

Large text files can exhaust the php memory limit when opened:

{"app":"PHP","method":"PUT","url":"/index.php/apps/text/session/9999578225/create","message":"Allowed memory size of 2147483648 bytes exhausted (tried to allocate 2900994904 bytes) at /var/www/nextcloud_32/lib/private/Files/Storage/Local.php#294"}

In the UI, this leads to a mostly white page with a generic error symbol at the bottom (screenshot below).

To Reproduce
Steps to reproduce the behavior:

1. Generate & upload text file larger than php memory limit, for example with:
   dd if=/dev/urandom bs=1M count=2048 | base64 > large.txt
2. Open file in the text editor, either as a logged in user or via a public share link

Expected behavior
Ideally - but probably difficult to implement -the file would be opened and displayed in chunks.

Alternatively, some configurable cutoff file size after which a clear error such as "file too large" is displayed to the user would be helpful.

For comparison, the onlyoffice editor has a configurable maxDownloadBytes parameter that defaults to 100M.

Screenshots

Server details:

• Nextcloud version: Nextcloud 31.0.8 EE, also reproduced with 32.0.0 CE.
• PHP Version: 8.2-fpm
• Database: MariaDB 10.11

Client details:

• Chrome 141 @ OpenSUSE Leap 16 (and others)

{"app":"PHP","method":"PUT","url":"/index.php/apps/text/session/9999578225/create","message":"Allowed memory size of 2147483648 bytes exhausted (tried to allocate 2900994904 bytes) at /var/www/nextcloud_32/lib/private/Files/Storage/Local.php#294"}

Failed to load resource: the server responded with a status of 500 ()

Start with the text session create endpoint in the logs and inspect lib/private/Files/Storage/Local.php around line 294 to trace how large files are opened. Reproduce with the provided dd command and verify that oversized files no longer exhaust PHP memory and instead produce a clear user-facing error; streaming remains a separate longer-term option.