Add configurable subpath support for UI deployment

[Copilot]

Enables deploying the UI at arbitrary paths (e.g., /feature, /app/v1) instead of root only.

Changes

Configuration

• Added SUBPATH environment variable / --subpath CLI flag
• Subpath normalized on startup (ensures leading /, strips trailing /)

Route Registration

• registerHandlers() prefixes all routes with configured subpath
• Affects: /, /features/*, /health

Template Updates

• index.gohtml: HTMX target uses {{.Subpath}}/features/list
• features_list.gohtml: Form actions use {{$.Subpath}}/features/{create,update,delete}

Helm Integration

• values.yaml: Added ui.subpath field
• ui-configmap.yaml: Exposes SUBPATH environment variable
• ui-deployment.yaml: Health probe paths dynamically constructed as {{ print (.Values.ui.subpath | default "") "/health" }}

Usage

# values.yaml
ui:
  subpath: /feature
  ingress:
    hosts:
      - paths:
          - path: /feature

Results in UI accessible at /feature/ with health checks at /feature/health.

Testing

Added TestSubpathSupport covering empty subpath, single-level (/feature), multi-level (/app/v1), and 404 behavior for incorrect paths.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• dl.google.com
  • Triggering command: /update-job-proxy /update-job-proxy service --proxy-cert /home/REDACTED/work/_temp/runtime-logs/mkcert/rootCA.pem --updater-env NODE_EXTRA_CA_CERTS=/usr/local/share/ca-certificates/dbot-ca.crt 9021231/b085/vet.cfg rg/toolchain@v0.0.1-go1.25.5.linux-amd64/pkg/tool/linux_amd64/link -p crypto/sha1 mpile rg/toolchain@v0.0.1-go1.25.5.linux-amd64/pkg/toosecurity (dns block)
  • Triggering command: /update-job-proxy /update-job-proxy -o br-a4a7c9798eb1 -j DROP C_RAIZ_FNMT-RCM_SERVIDORES_SEGUROS.pem rg/toolchain@v0./usr/share/ca-certificates/mozilla/Hongkong_Post_Root_CA_3.crt test /tmp/go-build121git -trimpath /usr/bin/gcc test -e oot_CA_2022.pem gcc /usr/bin/test 374748166136cca8/usr/sbin/iptables c /usr/bin/git test (dns block)
  • Triggering command: /update-job-proxy /update-job-proxy DROP /opt/go/bin/test/etc/ssl/certs/ce5e74ef.0 test -e cation_Authority.pem test est ertification_Aut/usr/bin/git git /bin/test test -e CA_v1.pem test /opt/go/bin/test zenpe.com.pem git endabot/../../bi-t test (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Support for subpath</issue_title>
<issue_description>I would like to put the frontend into a subpath like /feature, currently only / works.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Support for subpath #33

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