Act on the wj architectural review: races, limits, pool and contract gaps

Findings F2, F4, F5, F6, F7, F8, F9, F10, F11 and F13 from
wj-architectural-review.md. F1/F1a (the non-sargable LOWER pattern) and F3
(the warranty sync holding a pooled connection) are being handled separately
and are untouched here.

- A collector check-in that raced another for the same PC lost everything:
  the unique index on the application fingerprint raised, nothing caught it,
  and the whole check-in rolled back, discarding state, events and hardware,
  answering the agent with form copy meant for a person. The insert now runs
  in a savepoint, reconciles what the other transaction already wrote, one row
  per savepoint so a second collision skips a row rather than the batch, and
  the check-in commits with a warning. This is the shape the delete side of
  the same function already had.
- Enrollment is deliberately unauthenticated, so it now carries a per-address
  rate limit and a cap on pending requests, and the cap is a setting an admin
  can see and change. A flood can no longer bury the approval queue or grow
  the table without bound.
- The fleet alert poll no longer formats debug strings on every request.
- BusinessUnit is on the contract surface (0.34.0), so the endpoints plugin
  stops reaching into a core table with raw SQL.
- A test walks every asset type descriptor and proves the endpoint it names
  really refuses a caller without the declared permission.
- The plugin settings routes now need a permission; they were telling anyone
  which modules a site runs and where its components live.
- The connection pool is sized explicitly with a short timeout, and the
  arithmetic against the server's connection ceiling is written next to the
  worker count instead of being left to defaults nobody chose.
- Fleet alerts carry both the correct lowercase keys and the old camelCase
  pair. Trays older than 1.7.0 match keys case-sensitively and would have gone
  quiet on every PC not yet upgraded; the old pair goes when they are.
- The dev server proxy points at localhost again, with environment variables
  for the remote-box workflow, and one developer's address is out of the
  server certificate page.

agent/ShopDbEndpointAgent.Core/FleetAlertClient.cs

@@ -99,9 +99,9 @@ public sealed class FleetAlert
     private string title = "";
     private string message = "";
 
-    [JsonPropertyName("notificationId")] public int NotificationId { get; set; }
+    [JsonPropertyName("notificationid")] public int NotificationId { get; set; }
     [JsonPropertyName("type")] public string TypeName { get => typeName; set => typeName = value ?? ""; }
-    [JsonPropertyName("typeColor")] public string TypeColor { get => typeColor; set => typeColor = value ?? ""; }
+    [JsonPropertyName("typecolor")] public string TypeColor { get => typeColor; set => typeColor = value ?? ""; }
     [JsonPropertyName("title")] public string Title { get => title; set => title = value ?? ""; }
     [JsonPropertyName("message")] public string Message { get => message; set => message = value ?? ""; }
     [JsonPropertyName("timeout")] public int? Timeout { get; set; }
@@ -126,7 +126,7 @@ public sealed class FleetAlertList : List<FleetAlert>
 }
 
 // Deserializes the data array one element at a time. An element that fails
-// to bind, or has no usable notificationId, is recorded and skipped.
+// to bind, or has no usable notificationid, is recorded and skipped.
 public sealed class TolerantFleetAlertListConverter : JsonConverter<List<FleetAlert>>
 {
     public override List<FleetAlert>? Read(
@@ -146,7 +146,7 @@ public sealed class TolerantFleetAlertListConverter : JsonConverter<List<FleetAl
             {
                 var alert = element.RootElement.Deserialize<FleetAlert>(options);
                 if (alert is null || alert.NotificationId <= 0)
-                    list.Skipped.Add($"element {index}: missing notificationId");
+                    list.Skipped.Add($"element {index}: missing notificationid");
                 else
                     list.Add(alert);
             }