Allow empty virtual directory

[KharchenkoMaks]

The Docker configuration added support to set WPR_VIRTUAL_DIR to / or "" to serve the application from the root path in WebSpellChecker/wproofreader-docker#83. However, setting virtualDir: / (or virtualDir: "") in the Helm chart values.yaml produces malformed paths in the generated manifests.

Root cause

Path strings in deployment.yaml and NOTES.txt are constructed by directly interpolating .Values.virtualDir into a template string with hardcoded slashes:

path: /{{ .Values.virtualDir }}                  # becomes //
path: "/{{ .Values.virtualDir }}/api?cmd=status" # becomes ///api?cmd=status

printf ".../%s/" .Values.virtualDir              # becomes .../  /

Expected behavior

virtualDir value	Liveness path	Readiness path
wscservice (default)	/wscservice/	/wscservice/api?cmd=status
/ or ""	/	/api?cmd=status

What should be tested

• Default install (virtualDir: wscservice) — liveness and readiness probe paths render as /wscservice/ and /wscservice/api?cmd=status
• Root install (virtualDir: /) — probe paths render as / and /api?cmd=status, no double slashes
• Empty string install (virtualDir: "") — same as root, no double slashes
• NOTES.txt base URL renders correctly for all three cases above (no double slashes)
• WPR_VIRTUAL_DIR env var in the Deployment is passed to the container unchanged (not normalized)
• Service is reachable and returns a valid response at http://localhost/api?cmd=status when deployed with virtualDir: /