fix(netbird): use structured connection config for seed specs

[mikkeldamsgaard]

Summary

• Switch seed spec and PAT seed database connections from URL strings to Initium v2's structured config (host, port, user, password, name, options), eliminating URL-encoding issues when passwords contain special characters (@, %, :, etc.)
• Bump Initium from 1.2.0 to 2.0.0
• E2E tests now use password test%40pass to guard against regressions

Fixes #32

How to verify

# Unit tests
make test

# E2E (postgres backend with special-char password)
make e2e-postgres

# Rendered seed spec should show structured fields, not URL strings
helm template test charts/netbird \
  -f charts/netbird/ci/e2e-values-postgres.yaml \
  --set pat.enabled=true \
  --set pat.secret.secretName=netbird-pat \
  | grep -A12 'seed.yaml: |'

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