Phases 11, 12: mcrctl CLI tool and mcr-web UI

Phase 11 implements the admin CLI with dual REST/gRPC transport,
global flags (--server, --grpc, --token, --ca-cert, --json), and
all commands: status, repo list/delete, policy CRUD, audit tail,
gc trigger/status/reconcile, and snapshot.

Phase 12 implements the HTMX web UI with chi router, session-based
auth (HttpOnly/Secure/SameSite=Strict cookies), CSRF protection
(HMAC-SHA256 signed double-submit), and pages for dashboard,
repositories, manifest detail, policy management, and audit log.

Security: CSRF via signed double-submit cookie, session cookies
with HttpOnly/Secure/SameSite=Strict, TLS 1.3 minimum on all
connections, form body size limits via http.MaxBytesReader.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

web/templates/manifest_detail.html

@@ -0,0 +1,28 @@
+{{define "title"}}Manifest Detail{{end}}
+
+{{define "content"}}
+<h1>Manifest Detail</h1>
+
+{{if .Error}}
+<div class="error">{{.Error}}</div>
+{{else}}
+
+<div class="stats">
+    <div class="stat-card">
+        <div class="label">Digest</div>
+        <div class="value truncated" style="font-size: 0.875rem;">{{.Manifest.Digest}}</div>
+    </div>
+    <div class="stat-card">
+        <div class="label">Media Type</div>
+        <div class="value" style="font-size: 1rem;">{{.Manifest.MediaType}}</div>
+    </div>
+    <div class="stat-card">
+        <div class="label">Size</div>
+        <div class="value">{{formatSize .Manifest.Size}}</div>
+    </div>
+</div>
+
+<p><a href="/repositories/{{.RepoName}}">Back to {{.RepoName}}</a></p>
+
+{{end}}
+{{end}}