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

docs/data-sources/dns_records.md

@@ -37,3 +37,9 @@ data "dynu_dns_records" "records" {
   - `updated_on` (String)
   - `group` (String)
   - `host` (String)
+  - `priority` (Number) Priority for MX and SRV records.
+  - `weight` (Number) Weight for SRV records.
+  - `port` (Number) Port for SRV records.
+  - `flags` (Number) Flags for CAA records.
+  - `tag` (String) Tag for CAA records.
+  - `value` (String) Value for CAA records.