bump to v0.2.0: complete provider implementation with live-tested DNS record types

- DYNU_API_KEY env var fallback in provider config
- dynu_domain resource: add 9 computed attributes (unicode_name, ipv4/ipv6 flags,
  wildcard aliases, allow_zone_transfer, dnssec, created_on, updated_on)
- dynu_dns_records data source: add 6 type-specific fields (priority, weight,
  port, flags, tag, value)
- Fix normalizeRecordContentForState for MX/SRV/NS/PTR (read host field) and CAA
  (read value field) to avoid plan/state inconsistency
- Allow underscore-prefixed DNS labels in hostname validator (RFC 2782 SRV)
- Preserve plan/state hostname across create/update/read to prevent inconsistent
  result errors when API returns full FQDN for node_name-style records
- Update all version references from 0.1.0 to 0.2.0

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LFZyrmtKsezBwFWGTWsb2y

internal/provider/data_source_domain.go

@@ -18,7 +18,8 @@ var (
 	_ datasource.DataSourceWithConfigure = &domainDataSource{}
 )
 
-var hostnameValidator = regexp.MustCompile(`^([a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?\.)+[a-zA-Z]{2,}$`)
+// Allows underscore-prefixed labels (RFC 2782 SRV, RFC 6763 DNS-SD, etc.)
+var hostnameValidator = regexp.MustCompile(`^([a-zA-Z0-9_](?:[a-zA-Z0-9_-]{0,61}[a-zA-Z0-9_])?\.)+[a-zA-Z]{2,}$`)
 
 type domainDataSource struct {
 	clientProvider *providerData