[wleeaf]

The static file handler reads Range with sscanf("bytes=%ld-%ld") (HttpRequest::GetRange) and treats a last position of 0 as "to the end of the file". With httpd serving a 1000-byte file:

• Range: bytes=0-0 returns the whole file as 206 with Content-Range: bytes 0-999/1000. Clients often send bytes=0-0 to probe for range support and the file size, and they get 1000 bytes instead of 1.
• Suffix ranges (bytes=-10, bytes=-2000) always get 416, while bytes=-0 returns the whole file.
• When sscanf doesn't match (for example items=0-5 or bytes=abc), from is left uninitialized, and the response depends on whatever value it held.

defaultStaticHandler now parses the first range itself, following RFC 9110 section 14.1.2:

• It accepts first-last, first- and -length.
• A last position or a suffix that goes past the end is clamped to the file.
• A range that starts past the end still gets 416 with Content-Range: bytes */size.
• A Range header with another unit or an invalid range (for example 5-2) is ignored, and the whole file is sent with 200.

The small-range path now reads exactly the selected bytes, because HFile::readrange treats to = 0 as "to the end" as well. HttpRequest::GetRange and HFile::readrange are unchanged.

The new unittest/http_static_range_test (added to the Makefile, CMake and scripts/unittest.sh) serves a 10-byte file and checks 0-0, 5-, -3, -20, 10- and items=0-1. Without the change it fails on 0-0 (bytes 0-9/10). With the change it passes. Results with httpd for a 1000-byte file:

Range	before	after
bytes=0-0	206 0-999	206 0-0
bytes=-10	416	206 990-999
bytes=-2000	416	206 0-999
bytes=-0	206 0-999	416
items=0-5	416	200
Bytes=0-1	416	206 0-1

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