Add company logos and Portainer URL

Move SDT and Urban Switch logo SVGs to public/logos/ with
theme-aware variants. Add logo fields to Company config.
Update sidebar header to show theme-responsive logo.
Add Portainer URL (port 9000) to external tools config.

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

src/config/companies.ts

@@ -8,6 +8,10 @@ export interface Company {
   color: string;
   address: string;
   city: string;
+  logo?: {
+    light: string; // logo for light backgrounds
+    dark: string;  // logo for dark backgrounds
+  };
 }
 
 export const COMPANIES: Record<CompanyId, Company> = {
@@ -28,6 +32,10 @@ export const COMPANIES: Record<CompanyId, Company> = {
     color: '#6366f1',
     address: '',
     city: 'Cluj-Napoca',
+    logo: {
+      light: '/logos/logo-us-light.svg',
+      dark: '/logos/logo-us-dark.svg',
+    },
   },
   'studii-de-teren': {
     id: 'studii-de-teren',
@@ -37,6 +45,10 @@ export const COMPANIES: Record<CompanyId, Company> = {
     color: '#f59e0b',
     address: '',
     city: 'Cluj-Napoca',
+    logo: {
+      light: '/logos/logo-sdt-dark.svg',
+      dark: '/logos/logo-sdt-light.svg',
+    },
   },
   group: {
     id: 'group',