Match standard HTTP semantics of inclusive end value in Range and Content-Range headers

[eddyashton]

This is take 2 at #7626. Previously implemented in #7632, but reverted in #7641 due to introducing an LTS compat failure. This should only be merged once we're sure LTS compat is green (multiple long_test runs).

[Copilot]

Pull request overview

This pull request fixes the HTTP Range and Content-Range header handling to match standard HTTP semantics where the range end value is inclusive (e.g., "bytes=0-9" means 10 bytes, from 0 to 9 inclusive). This is a second attempt at resolving issue #7626, after the first attempt in #7632 was reverted in #7641 due to LTS compatibility issues.

Changes:

• Converted Range header parsing and Content-Range header emission to use HTTP-standard inclusive end values
• Maintained exclusive range end values internally for idiomatic C++ processing with conversions at I/O boundaries
• Added comprehensive test coverage for various range scenarios including edge cases

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
include/ccf/http_consts.h	Adds RANGE constant for consistent header name usage
src/node/rpc/file_serving_handlers.h	Updates server-side range request handling to parse inclusive end values from headers, process with exclusive values internally, and emit inclusive values in responses
src/snapshots/fetch.h	Updates client-side range request handling to send inclusive end values in requests and parse inclusive values from Content-Range responses
tests/e2e_operations.py	Adds comprehensive tests for inclusive range semantics including single-byte ranges, full ranges, partial ranges, open-ended ranges, and negative offsets