fix(landing-page): diagram links - use bundle path, not docs/diagrams/

Architecture diagram links on the deployed landing page returned 404
because the generator emitted 'docs/diagrams/<file>.svg' (repo-relative)
while validate.yml/release.yml deploy the SVGs to '<bundle>/diagrams/'.

Use the same bundle-relative pattern as coverage/cppcheck/traceability
(emit just 'diagrams/<file>.svg').

Also translates two remaining German comments in release.yml
('CI-generierte Artefakte', 'Source-Code zum Anklicken...').

.gitea/workflows/release.yml

@@ -59,7 +59,7 @@ jobs:
           # Landing page in the bundle root
           cp build/index.html               "$BUNDLE/index.html"
 
-          # CI-generierte Artefakte
+          # CI-generated artefacts
           cp -r build/coverage-html/*        "$BUNDLE/coverage/"          2>/dev/null || true
           cp -r docs/traceability/*          "$BUNDLE/traceability/"
           cp -r docs/diagrams/*              "$BUNDLE/diagrams/"
@@ -69,7 +69,7 @@ jobs:
           cp    build/test-report.html       "$BUNDLE/reports/"           2>/dev/null || true
           cp    build/test-report.md         "$BUNDLE/reports/"           2>/dev/null || true
 
-          # Source-Code zum Anklicken aus dem Bundle (begrenzt auf das wichtigste)
+          # Source code from the bundle (limited to the essentials)
           cp -r src/*.c src/*.h             "$BUNDLE/src/"             2>/dev/null || true
           cp -r src/stubs                   "$BUNDLE/src/"             2>/dev/null || true