feat: IPv6 support and multi-IP per node (closes #60)

- maskIp handles IPv6 addresses (masks second and last group)
- maskIp handles comma-separated IP strings (masks each address)
- Add splitIps() helper to parse comma-separated IP field
- Add primaryIp() helper used by status checker (first IP wins)
- BaseNode renders each IP on its own line when comma-separated
- NodeModal placeholder shows comma-separated example
- Backend status_checker uses only first IP for connectivity checks
- Expand maskIp test suite: IPv6, comma-separated, splitIps, primaryIp

frontend/src/utils/__tests__/maskIp.test.ts

@@ -1,7 +1,8 @@
 import { describe, it, expect } from 'vitest'
-import { maskIp } from '../maskIp'
+import { maskIp, splitIps, primaryIp } from '../maskIp'
 
 describe('maskIp', () => {
+  // IPv4
   it('masks last two octets of a standard IPv4', () => {
     expect(maskIp('192.168.1.115')).toBe('192.168.XX.XX')
   })
@@ -11,9 +12,61 @@ describe('maskIp', () => {
     expect(maskIp('172.16.254.1')).toBe('172.16.XX.XX')
   })
 
-  it('passes through non-IPv4 strings unchanged', () => {
+  // IPv6
+  it('masks second group and last group of an IPv6 address', () => {
+    expect(maskIp('2001:db8::1')).toBe('2001:XX::XX')
+  })
+
+  it('masks a full IPv6 address', () => {
+    expect(maskIp('fe80:0000:0000:0000:0202:b3ff:fe1e:8329')).toBe('fe80:XX:0000:0000:0202:b3ff:fe1e:XX')
+  })
+
+  it('masks loopback IPv6', () => {
+    // ::1 splits into ['', '', '1'] — groups[1] and last are masked
+    expect(maskIp('::1')).toBe(':XX:XX')
+  })
+
+  // Comma-separated
+  it('masks all IPs in a comma-separated string', () => {
+    expect(maskIp('192.168.1.1, 2001:db8::1')).toBe('192.168.XX.XX, 2001:XX::XX')
+  })
+
+  it('handles comma-separated without spaces', () => {
+    expect(maskIp('10.0.0.1,10.0.0.2')).toBe('10.0.XX.XX, 10.0.XX.XX')
+  })
+
+  // Edge cases
+  it('passes through non-IP strings unchanged', () => {
     expect(maskIp('hostname')).toBe('hostname')
-    expect(maskIp('fe80::1')).toBe('fe80::1')
     expect(maskIp('')).toBe('')
   })
 })
+
+describe('splitIps', () => {
+  it('returns array of trimmed IPs', () => {
+    expect(splitIps('192.168.1.1, 2001:db8::1')).toEqual(['192.168.1.1', '2001:db8::1'])
+  })
+
+  it('returns single-element array for single IP', () => {
+    expect(splitIps('10.0.0.1')).toEqual(['10.0.0.1'])
+  })
+
+  it('returns empty array for empty string', () => {
+    expect(splitIps('')).toEqual([])
+    expect(splitIps('   ')).toEqual([])
+  })
+})
+
+describe('primaryIp', () => {
+  it('returns first IP from comma-separated string', () => {
+    expect(primaryIp('192.168.1.1, 2001:db8::1')).toBe('192.168.1.1')
+  })
+
+  it('returns the only IP when single', () => {
+    expect(primaryIp('10.0.0.1')).toBe('10.0.0.1')
+  })
+
+  it('returns empty string for empty input', () => {
+    expect(primaryIp('')).toBe('')
+  })
+})