Replace trivial calls to snprintf with safe_strcpy

[dpw13]

This PR replaces two different cases of snprintf() with the simpler safe_strcpy():

1. snprintf(dest, size, "%s", string): These are safe but unnecessarily complex when a string is being copied.
2. snprintf(dest, size, string): These are safe if the string is constant and doesn't contain any format specifiers, but is still unnecessarily complex.

There are other instances in the codebase where snprintf is still used:

• When nearby regions of code actually use format specifiers. I've kept the snprintf to match the nearby code for clarity.
• When the return value of snprintf is used, e.g. to increment a pointer. We could modify safe_strcpy() to return the length of the string copied, or perhaps create a modified safe_strcat() that carries along an offset. This PR is only intended to replace trivial calls though, so I'm deferring changing these to a future update if/when we decide such a change is worthwhile.

[Copilot]

Pull request overview

This PR simplifies several string-copy sites by replacing trivial snprintf() usages with safe_strcpy(), reducing verbosity and eliminating any residual risk of accidental format-string interpretation in copy-only cases.

Changes:

• Replaced snprintf(dst, size, "%s", src)-style copies with safe_strcpy(dst, src, size, 0) across web, video, database, and core modules.
• Updated includes where needed to use the string utility header (utils/strings.h).

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/web/thumbnail_thread.c	Uses safe_strcpy for input/output path copies and adds required include.
src/web/api_handlers_system.c	Uses safe_strcpy for copy-only version/detail fields.
src/web/api_handlers_streams_test.c	Uses safe_strcpy for a constant error message.
src/web/api_handlers_recordings_batch_download.c	Uses safe_strcpy for ZIP entry name copy.
src/video/onvif_discovery.c	Uses safe_strcpy to copy inet_ntoa() results into a local buffer.
src/video/onvif_discovery_thread.c	Reorders project includes and uses safe_strcpy for IP address string copies.
src/video/hls/hls_unified_thread.c	Uses safe_strcpy for local stream-name copy used in logging/cleanup.
src/video/go2rtc/go2rtc_api.c	Uses safe_strcpy for JSON string extraction into caller-provided buffers.
src/database/db_recordings.c	Uses safe_strcpy for constant SQL fragments prior to concatenation.
src/core/config.c	Uses safe_strcpy for default config string initialization.

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