Add local puppet forge (#145)

Puppet modules can only be proxied from a remote Forge; there is nowhere to publish internal modules for puppet module install, r10k and g10k.

- add puppet local uploads at <owner>-<module>-<version>.tar.gz, rejecting existing versions
- record each release's metadata.json, md5 and sha256 in a puppet_metadata table, streaming the tarball under size caps
- serve Forge v3 /v3/modules, paginated /v3/releases, /v3/releases/<slug> and /v3/files
- add an e2e-docker case driving real r10k and puppet module install
- document local puppet in README and UI usage snippets

Reviewed-on: #145
Co-authored-by: unkin-agent <unkin-agent@unkin.net>
Co-committed-by: unkin-agent <unkin-agent@unkin.net>

ui/src/components/UsageInstructions.tsx

@@ -262,11 +262,21 @@ index = "sparse+${proxy}/"`,
     case 'puppet':
       return [
         {
-          title: 'Install a module from the Forge proxy',
+          title: isLocal ? 'Install a module from this forge' : 'Install a module from the Forge proxy',
           language: 'bash',
           code: `puppet module install <author>-<module> \\
-  --module_repository ${proxy}`,
+  --module_repository ${isLocal ? `${url}/api/v1/local/${name}` : proxy}`,
         },
+        ...(isLocal
+          ? [
+              {
+                title: 'Publish a module (versions are immutable)',
+                language: 'bash',
+                code: `puppet module build && curl -fsSL --upload-file pkg/<author>-<module>-<version>.tar.gz \\
+  ${url}/api/v2/remotes/${name}/files/<author>-<module>-<version>.tar.gz`,
+              },
+            ]
+          : []),
       ];
 
     case 'deb':