feat: add Docker deployment, web installer, and local test environment

- Multi-stage Dockerfiles for API (NestJS) and Web (Next.js standalone)
- docker-compose.prod.yml: full production stack (postgres, redis, keycloak,
  api, web) with optional Caddy/Let's Encrypt via --profile ssl
- docker-compose.local.yml: identical local test stack, all ports exposed
- docker/postgres/init.sql: auto-creates tos_app DB on first start
- Caddyfile: reverse proxy for app domain + auth subdomain
- install.sh: interactive installer (domain, SSL mode, secret generation)
- NestJS SetupModule: @Public() endpoints for /setup/status, /setup/admin,
  /setup/branding, /setup/complete with setup-token guard
- Web installer: 4-step flow (system check, admin creation, branding, complete)
  at /[locale]/setup/* with public middleware bypass
- i18n: installer namespace added to de.json and en.json
- CORS: x-setup-token header allowed in main.ts

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

apps/web/messages/en.json

@@ -1073,5 +1073,63 @@
     "saveError": "Failed to save settings",
     "requiresRestart": "Change requires a backend restart",
     "save": "Save"
+  },
+  "installer": {
+    "title": "tOS Setup",
+    "setupComplete": "Setup Complete",
+    "notAccessible": "After setup, this area will no longer be accessible.",
+    "steps": {
+      "systemCheck": "System Check",
+      "adminSetup": "Admin Account",
+      "branding": "Branding",
+      "complete": "Complete"
+    },
+    "systemCheck": {
+      "title": "System Check",
+      "description": "Checking all services for availability.",
+      "api": "API Server",
+      "database": "Database",
+      "keycloak": "Authentication",
+      "online": "Online",
+      "offline": "Unreachable",
+      "checking": "Checking...",
+      "continue": "Continue Setup",
+      "alreadyComplete": "Setup has already been completed.",
+      "redirecting": "Redirecting to dashboard..."
+    },
+    "adminSetup": {
+      "title": "Create Admin Account",
+      "description": "Create the first administrator account for tOS.",
+      "firstName": "First Name",
+      "lastName": "Last Name",
+      "email": "Email Address",
+      "password": "Password",
+      "passwordConfirm": "Confirm Password",
+      "passwordMismatch": "Passwords do not match",
+      "passwordTooShort": "Minimum 8 characters required",
+      "createAccount": "Create Account",
+      "creating": "Creating..."
+    },
+    "branding": {
+      "title": "Configure Branding",
+      "description": "Customize tOS for your company.",
+      "appName": "App Name",
+      "appNamePlaceholder": "tOS",
+      "companyName": "Company Name",
+      "companyNamePlaceholder": "My Company Inc.",
+      "logoUrl": "Logo URL",
+      "logoUrlPlaceholder": "https://example.com/logo.png",
+      "logoPreview": "Logo Preview",
+      "save": "Save & Continue",
+      "saving": "Saving...",
+      "skip": "Skip"
+    },
+    "complete": {
+      "title": "Setup Complete!",
+      "description": "tOS has been successfully set up and is ready to use.",
+      "completing": "Completing setup...",
+      "toDashboard": "Go to Dashboard",
+      "toLogin": "Go to Login"
+    }
   }
 }