fix(rpm): restore lowercase package Name (unbreak Source0 / build)

ae51276 capitalized the spec Name to `Punktfunk` in a branding sweep, but
build-rpm.sh writes the git-archive tarball as lowercase `punktfunk-<v>.tar.gz`
(prefix dir likewise). `%{name}` drives Source0, `%autosetup -n`, and the
`%{_datadir}/%{name}` install path, so the capital-P both broke the build
(rpmuncompress: `Punktfunk-<v>.tar.gz: No such file`) and would have renamed the
published package + its share dir vs every prior release. RPM names are lowercase
by convention; v0.3.x / v0.4.0 shipped as `punktfunk`.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

packaging/rpm/punktfunk.spec

@@ -16,7 +16,7 @@
 # only new runtime bits are ffmpeg-libs (RPM Fusion) + opus + libei.
 ################################################################################
 
-Name:           Punktfunk
+Name:           punktfunk
 # Version/Release are overridable so CI can stamp a rolling snapshot: a canary main build passes
 #   --define "pf_version 0.3.0" --define "pf_release 0.ci42.gdeadbee"
 # (Release starting "0." sorts BEFORE the eventual "1" release; the canary base stays one minor