Fix passkey RPID mismatch across environments

Derive ServerDomain and Origin from the incoming HTTP request instead of
appsettings.json, so WebAuthn works on localhost, dev, and production
without any environment-specific configuration. Removed IFido2 from DI
and the Fido2 appsettings block — PasskeyController instantiates Fido2
per-request via BuildFido2().

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

src/PowderCoating.Web/appsettings.json

@@ -68,12 +68,6 @@
       "Enterprise": "price_enterprise_monthly_id_here"
     }
   },
-  "Fido2": {
-    "ServerDomain": "localhost",
-    "ServerName": "Powder Coating Logix",
-    "Origins": [ "https://localhost:58461", "http://localhost:58462" ],
-    "TimestampDriftTolerance": 300
-  },
   "Storage": {
     "ConnectionString": "DefaultEndpointsProtocol=https;AccountName=powdercoatingappdev;AccountKey=DN3eVfhytXb7aBC0md9h/6jE0Uzg6FJ+PK6MFc772qyqpf0kgTeXH0C2VCBBun9PiuItPd9CDKTP+ASthFCuCg==;EndpointSuffix=core.windows.net",
     "Containers": {