pyln-proto: update coincurve to commit 7829b29c08ebb1cc80386a1cdaf8c2243c4ef5c5

```
 DEBUG: DEBUG ERROR: Use build.verbose instead of cmake.verbose for scikit-build-core >= 0.10
 DEBUG:   × Failed to build `coincurve==20.0.0`
 DEBUG:   ├─▶ The build backend returned an error
 DEBUG:   ╰─▶ Call to `hatchling.build.build_wheel` failed (exit status: 7)
 DEBUG:
 DEBUG:       [stderr]
 DEBUG:       ERROR: Use build.verbose instead of cmake.verbose for scikit-build-core
 DEBUG:       >= 0.10
 DEBUG:
 DEBUG:
 DEBUG: hint: `coincurve` (v20.0.0) was included because `testpluguv` (v0.1.0) depends on `pyln-client` (v26.6.2) which depends on `pyln-proto` (v26.6.2) which depends on `coincurve`
```

This error is caused because coincurve v20 depends on scikit-build-core>=0.9.0 and they did a new release where
using cmake.verbose is no longer a warning but an error. coincurve v21 is using the correct build.verbose but is not
working with python 3.14. So we update coincurve to current master until the next release.

Changelog-None

Author: daywalker90

contrib/pyln-proto/pyproject.toml

@@ -11,11 +11,14 @@ requires-python = ">=3.10,<4.0"
 dependencies = [
     "base58>=2.1.1",
     "bitstring>=4.3.0",
-    "coincurve==20.0.0",
+    "coincurve",
     "cryptography>=46",
     "PySocks>=1"
 ]
 
+[tool.uv.sources]
+coincurve = { git = "https://github.com/ofek/coincurve.git", rev = "7829b29c08ebb1cc80386a1cdaf8c2243c4ef5c5" }
+
 [dependency-groups]
 dev = [
   "pytest>=8.0.0"