hub v0.15.0: Phase 2 managed updates — per-customer controller-version floor

Operator sets a minimum controller version (FLOOR), per-customer defaulting to a
global floor; the report ACK returns the effective floor + latest_version so the
controller auto-updates to the floor when below it (latest stays the opt-in button).

- store: min_controller_version column + hub_settings global floor + Effective/
  Get/SetGlobal/SetMin resolution + config/env DEFAULT_MIN_CONTROLLER_VERSION
- handler: report ACK {min_controller_version, latest_version}; LatestVersionProvider
- web: global floor editor + per-customer override form + Floor column (English)
- tests: floor resolution + ACK + render; override-precedence red-proof verified

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FSZmmSFVzGwEzhYmxbkgBK

hub/internal/web/templates/configs.html

@@ -20,10 +20,28 @@
 
         {{if .Flash}}
         <div class="flash flash-success">
-            {{if eq .Flash "deleted"}}Customer configuration deleted.{{end}}
+            {{if eq .Flash "deleted"}}Customer configuration deleted.
+            {{else if eq .Flash "floor_set"}}Controller-version floor saved.
+            {{else if eq .Flash "floor_invalid"}}Invalid version — use X.Y.Z (or blank to clear).
+            {{end}}
         </div>
         {{end}}
 
+        <!-- Phase 2 managed updates: global controller-version floor -->
+        <div class="card" style="margin-bottom: 1rem; padding: 1rem; border: 1px solid #334155; border-radius: 8px;">
+            <h2 style="margin: 0 0 0.5rem;">Managed updates — global floor</h2>
+            <p style="font-size: 0.85em; color: #94a3b8; margin: 0 0 0.5rem;">
+                The minimum controller version every box auto-updates to (unless a per-customer override is set).
+                Boxes below the floor update on their next report — no customer action. Blank = no global floor.
+            </p>
+            <form method="POST" action="/configs/global-floor" style="display: flex; gap: 0.5rem; align-items: center; flex-wrap: wrap;">
+                {{.CSRFField}}
+                <input type="text" name="min_controller_version" value="{{.GlobalFloor}}" placeholder="e.g. 0.86.0 (blank = none)" style="padding: 0.3em 0.5em; width: 14em;">
+                <button class="btn btn-sm" type="submit">Save global floor</button>
+                <span style="font-size: 0.85em; color: #cbd5e1;">Current: {{if .GlobalFloor}}<code>v{{.GlobalFloor}}</code>{{else}}<span class="text-muted">unset</span>{{end}}</span>
+            </form>
+        </div>
+
         <div style="display: flex; justify-content: space-between; align-items: center; margin-bottom: 1rem;">
             <h2 style="margin: 0;">Customers</h2>
             <a href="/configs/new" class="btn">+ Add Customer</a>
@@ -43,6 +61,7 @@
                     <th>Domain</th>
                     <th>Status</th>
                     <th>Version</th>
+                    <th>Floor</th>
                     <th>Config</th>
                 </tr>
             </thead>
@@ -64,6 +83,10 @@
                         {{end}}
                     </td>
                     <td>{{if .ControllerVersion}}<code>{{.ControllerVersion}}</code>{{else}}<span class="text-muted">—</span>{{end}}</td>
+                    <td>
+                        {{if .EffectiveFloor}}<code>v{{.EffectiveFloor}}</code>{{if .FloorOverride}}<span class="text-muted" style="font-size:0.8em;"> (override)</span>{{end}}{{if .BelowFloor}}<span style="color:#f59e0b;" title="below floor — will auto-update"> ●</span>{{end}}
+                        {{else}}<span class="text-muted">—</span>{{end}}
+                    </td>
                     <td>
                         {{if .HasConfig}}
                         <span class="config-badge config-badge-managed">MANAGED</span>