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/Pages/Design/ApiMethodForm.razor

@@ -38,7 +38,9 @@
                 </div>
                 <div class="mb-3">
                     <label class="form-label">Script</label>
-                    <MonacoEditor Value="@_script" ValueChanged="@(v => _script = v)" Language="csharp" Height="320px" />
+                    <MonacoEditor Value="@_script" ValueChanged="@(v => _script = v)"
+                                  Language="csharp" Height="320px"
+                                  DeclaredParameters="@ScriptParameterNames.Parse(_params)" />
                 </div>
 
                 @if (_formError != null)

src/ScadaLink.CentralUI/Components/Pages/Design/SharedScriptForm.razor

@@ -39,7 +39,9 @@
                 </div>
                 <div class="mb-2">
                     <label class="form-label small">Code</label>
-                    <MonacoEditor Value="@_formCode" ValueChanged="@(v => _formCode = v)" Language="csharp" Height="320px" />
+                    <MonacoEditor Value="@_formCode" ValueChanged="@(v => _formCode = v)"
+                                  Language="csharp" Height="320px"
+                                  DeclaredParameters="@ScriptParameterNames.Parse(_formParameters)" />
                 </div>
                 @if (_formError != null)
                 {

src/ScadaLink.CentralUI/Components/Pages/Design/TemplateEdit.razor

@@ -654,7 +654,10 @@
                         </div>
                         <div class="col-12">
                             <label class="form-label">Code</label>
-                            <MonacoEditor Value="@_scriptCode" ValueChanged="@(v => _scriptCode = v)" Language="csharp" Height="320px" />
+                            <MonacoEditor Value="@_scriptCode" ValueChanged="@(v => _scriptCode = v)"
+                                          Language="csharp" Height="320px"
+                                          DeclaredParameters="@ScriptParameterNames.Parse(_scriptParameters)"
+                                          SiblingScripts="@(_scripts.Select(s => s.Name).ToArray())" />
                         </div>
                         @if (_scriptFormError != null)
                         {