fix: plumb skiplock parameter for VMs, force for containers

VM removal: add skiplock=1 parameter when -Force is specified. PVE honors it
for root@pam only; non-root callers receive 403 errors. Updated help text.

Container removal: map -Force to force=1 (LXC-specific parameter for forcing
removal of running containers). Containers do not support skiplock.

Also: clarified class and parameter documentation to remove false claims about
-Force suppressing confirmation (it does not).

Fixes #136. Addresses correctness reviewer findings.

tests/PSProxmoxVE.Core.Tests/Services/VmServiceTests.cs

@@ -56,7 +56,7 @@ namespace PSProxmoxVE.Core.Tests.Services
                 "powershell.exe", new[] { "-NoProfile", "-Command", "echo hi" });
 
             Assert.NotNull(captured);
-            // Args are argv, not STDIN — "input-data" must never be emitted.
+            // Args are argv, not STDIN - "input-data" must never be emitted.
             Assert.DoesNotContain(captured!, kvp => kvp.Key == "input-data");
         }