fix: add uri strip_prefix /forge to Caddyfile generator — Forgejo routes 404 without it (completes #1080)

The /forge/* handle block in the Caddyfile generator was missing the
"uri strip_prefix /forge" directive. Without it, Caddy forwards
/forge/foo → forgejo:3000/forge/foo, Forgejo's router doesn't match,
and returns 404. Adding strip_prefix makes the prefix transparent to
Forgejo while ROOT_URL still governs link generation in HTML.

Also fixes nomad/jobs/edge.hcl (Nomad-rendered Caddyfile template)
and .woodpecker/edge-subpath.yml (CI mock Caddyfile) for consistency.

Same pattern as the /staging/* strip_prefix added in #1079.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.woodpecker/edge-subpath.yml

@@ -59,6 +59,7 @@ steps:
           echo ''
           echo '    # Reverse proxy to Forgejo'
           echo '    handle /forge/* {'
+          echo '        uri strip_prefix /forge'
           echo '        reverse_proxy 127.0.0.1:3000'
           echo '    }'
           echo ''

nomad/jobs/edge.hcl

@@ -151,6 +151,7 @@ EOT
 
     # Reverse proxy to Forgejo
     handle /forge/* {
+        uri strip_prefix /forge
         reverse_proxy 127.0.0.1:3000
     }