feat(ui/scripts): SCADA-specific Monaco extensions

Wave 3 of the Monaco/Roslyn integration. Adds the four extensions
agreed in the design Q&A:

  1. Parameters["..."] keys — when the cursor is inside a string
     literal that's the index of a Parameters[] element-access,
     completions return the parameter names declared in the form's
     ParameterListEditor.
  2. CallShared("...") names — when the cursor is inside a string
     literal argument to a CallShared(...) invocation, completions
     return the names of all shared scripts (resolved server-side
     via SharedScriptService).
  3. CallScript("...") names — same shape, but uses sibling-script
     names passed from the form (TemplateEdit's _scripts list).
  4. Forbidden-API diagnostic — squiggles uses of the documented
     script trust model bans: System.IO / Diagnostics / Reflection /
     Net / Threading.Thread namespaces, plus the named types File,
     Directory, Process, Thread, Socket, etc. New diagnostic codes
     SCADA001 (using directive) and SCADA002 (type identifier).

ScriptAnalysisService gains a SharedScriptService dependency
(scoped, hence the analyzer is now scoped too); CompletionsRequest
carries DeclaredParameters and SiblingScripts; Complete is now async.

MonacoEditor.razor exposes DeclaredParameters / SiblingScripts
parameters plus a [JSInvokable] GetContext() so the JS side asks
for the latest form state on every completion request. The
provider in monaco-init.js looks up the owning editor from the
internal editors map and forwards the context.

ScriptParameterNames helper parses the ParameterListEditor JSON
into a name list — used by SharedScriptForm, ApiMethodForm, and
TemplateEdit's Add-Script form to populate the Monaco context.

Smoke-verified via direct fetch + Monaco trigger:
  - var x = Parameters["  →  popup: "name" (declared parameter)
  - var y = CallShared("  →  popup: GetWeather, Greet
  - using System.IO;      →  SCADA001 squiggle
  - Process.Start(...)    →  SCADA002 squiggle
  - File.ReadAllText(...) →  SCADA002 squiggle

Also fixed: ScriptAnalysisService scoped (was singleton, broke DI
because SharedScriptService is scoped); JS normalizes Pascal-case
context keys from Blazor's record serialization to camel-case for
the request body.

src/ScadaLink.CentralUI/Components/Shared/ScriptParameterNames.cs

@@ -0,0 +1,29 @@
+using System.Text.Json;
+
+namespace ScadaLink.CentralUI.Components.Shared;
+
+/// <summary>
+/// Parses the parameter-definitions JSON written by ParameterListEditor and
+/// returns the declared parameter names. Used by script-edit pages to feed
+/// the Monaco editor's Parameters["..."] completion provider.
+/// </summary>
+public static class ScriptParameterNames
+{
+    public static IReadOnlyList<string> Parse(string? json)
+    {
+        if (string.IsNullOrWhiteSpace(json)) return Array.Empty<string>();
+        try
+        {
+            using var doc = JsonDocument.Parse(json);
+            if (doc.RootElement.ValueKind != JsonValueKind.Array) return Array.Empty<string>();
+            return doc.RootElement.EnumerateArray()
+                .Select(e => e.TryGetProperty("name", out var n) ? n.GetString() ?? "" : "")
+                .Where(s => !string.IsNullOrEmpty(s))
+                .ToList();
+        }
+        catch
+        {
+            return Array.Empty<string>();
+        }
+    }
+}