security: fix 27 vulnerabilities + UI integration (Issues tab, project nav, validation)

Security fixes (27 vulnerabilities across 20 files):
CRITICAL:
- MediaManager: whitelist mediable types prevents RCE via class instantiation
- MediaManager/OfflineSyncController: IDOR fixes, remove Auth::id()??1 fallback
- ClientProjects: verify project ownership on all mutations (IDOR)
- CompanyManagement: Admin role check on mount() and mutations (auth bypass)
- ProjectMap: scope feature/template lookups to current project (IDOR x5)
- PhaseList/TemplateManager/LayerManager: scope mutations to owned resources (IDOR)
- ProjectEditTabs: Gate::authorize on mount() and updateProject()
- routes/web.php: reports routes moved inside can:manage all middleware (auth bypass)

MEDIUM:
- layer-manager: escapeHtml() on Leaflet popup interpolations (XSS)
- MediaManager: server-side MIME validation + 50MB limit
- ProjectList/ProjectUsers/ProjectCompanies/PhaseProgress: auth checks added
- AdminUsers/ReportsDashboard/ExportController: role/permission checks added

LOW:
- config/session.php: secure cookie tied to production env
- OfflineSyncController: sanitize storage path (path traversal)

UI integration:
- project-map: Issues tab (4th) with open-count badge
- project-map: project navigation bar (Dashboard/Map/Gantt/Report/Issues)
- project-dashboard: action buttons for Map/Gantt/Report/Issues
- project-form: validation error summary + per-field @error spans
- template-manager: validation error display

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

app/Livewire/ProjectCompanies.php

@@ -17,6 +17,10 @@ class ProjectCompanies extends Component
 
     public function mount(Project $project)
     {
+        $user = Auth::user();
+        if (!$user->hasRole('Admin') && !$project->users()->where('user_id', $user->id)->exists()) {
+            abort(403);
+        }
         $this->project = $project;
         $this->loadCompanies();
     }
@@ -65,6 +69,11 @@ class ProjectCompanies extends Component
 
     public function changeRole($companyId, $role)
     {
+        $user = Auth::user();
+        if (!$user->can('assign users') && !$user->hasRole('Admin')) {
+            session()->flash('error', 'Sin permisos.');
+            return;
+        }
         if (!in_array($role, ['owner', 'constructor', 'subcontractor', 'consultant', 'supplier', 'other'])) return;
 
         $this->project->companies()->updateExistingPivot($companyId, [