Remove survMisc dependency, implement weighted log-rank tests internally

[kassambara]

Summary

• Replace survMisc::ten() and survMisc::comp() with a self-contained internal weighted log-rank test implementation (R/weighted_logrank.R, ~130 lines of base R)
• survMisc is at risk of CRAN archival (last updated April 2022); this removes the only dependency on it
• All 6 weight methods (log-rank, Gehan-Breslow, Tarone-Ware, Peto-Peto, modified Peto-Peto, Fleming-Harrington) plus test-for-trend continue to work identically — validated against survMisc output

Changes

File	Change
R/weighted_logrank.R	New internal .weighted_logrank_test() function
R/surv_pvalue.R	Replace ten()/comp() block with call to new internal function
R/utilities.R	Remove @importFrom survMisc ten comp
DESCRIPTION	Remove survMisc from Imports
NAMESPACE	Auto-regenerated, survMisc imports removed
R/ggsurvplot.R, R/ggurvplot_arguments.R	Replace \link[survMisc]{comp} with plain text
vignettes/	Remove survMisc references
NEWS.md	Add entry under Major changes
tests/testthat/test-surv_pvalue.R	New tests covering all weight methods, multi-group, trend

Test plan

• devtools::test() — 42 tests pass, 0 failures
• devtools::check(vignettes = FALSE) — 0 errors, 0 warnings
• Validated new implementation against survMisc reference values for all 6 methods, 2-group, 3+ group, and test-for-trend cases