Add lazy API version negotiation (v4 -> v3 fallback) with -ApiVersion override

- Endpoint registry now stores ordered candidate lists per logical operation; Get/TryGet preserve prior behavior, new GetCandidates(name) exposes the ladder. Added v3 fallbacks (/api/v3/secrets/raw and /api/v3/secrets/raw/{secretName}) after v4. - InfisicalConnection gains PinnedApiVersion and a ResolvedEndpointVersions cache so the chosen version sticks for the session. - InfisicalSecretsClient.SendWithVersionFallback walks candidates in pin -> cached -> registry order, falls back on routing-style failures (404 without an Infisical JSON envelope, 405, or 400 mentioning workspaceId/projectSlug) when no version is pinned, and surfaces real application errors immediately. - Get-InfisicalSecret(s) expose -ApiVersion; Connect-Infisical sets PinnedApiVersion only when -ApiVersion is explicitly bound on the command line (env-var/default values do not pin). - Logger.Error routes via WriteWarning to avoid premature terminating errors that masked InfisicalApiException details; EnsureSuccess no longer redacts non-2xx bodies so server error envelopes are visible. - InfisicalSecretsClient sends both projectId and workspaceId so it works against both new and legacy server-side validators.

src/PSInfisicalAPI/Connections/InfisicalConnection.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Security;
 using PSInfisicalAPI.Models;
 
@@ -8,6 +9,7 @@ namespace PSInfisicalAPI.Connections
     {
         public Uri BaseUri { get; set; }
         public string ApiVersion { get; set; }
+        public string PinnedApiVersion { get; set; }
         public InfisicalAuthType AuthType { get; set; }
         public string OrganizationId { get; set; }
         public string ProjectId { get; set; }
@@ -17,6 +19,8 @@ namespace PSInfisicalAPI.Connections
         public DateTimeOffset? ExpiresAtUtc { get; set; }
         public bool IsConnected { get; set; }
 
+        public Dictionary<string, string> ResolvedEndpointVersions { get; } = new Dictionary<string, string>(StringComparer.Ordinal);
+
         internal SecureString AccessToken { get; set; }
 
         public override string ToString()