Apply code-review fixes: identity/pagination, load races, TLS pin, leaks

Addresses a multi-agent code review (26 confirmed findings + a URLSession
leak) across correctness, concurrency, security, and cleanup:

- MongoDocument.id: deterministic fallback (was UUID() on every access) to stop
  SwiftUI List/ForEach identity churn; getAll pagination drives its cursor off
  the real _id via documentId, so a missing _id stops paging instead of looping
  on a fabricated cursor.
- View models: per-load generation guard (+ captured-tab guard on ONU detail)
  so a cancelled or overlapping load can't commit stale results or land data on
  the wrong tab.
- JSONValue.intValue: guard Int(d) against NaN/inf/out-of-range (crash).
- ServerTrustEvaluator: hash the real SubjectPublicKeyInfo (prepend the
  algorithm-specific ASN.1 SPKI header) so a standard openssl-captured
  public-key pin actually matches; unknown key types fail closed.
- AppEnvironment.configure: clear stale cookies + Keychain creds on host change.
- FirmwareFile.isCompatible: empty metadata no longer passes as compatible-for-all.
- APIClient: invalidate URLSession on deinit (per-configure/probe leak).
- Dashboard best-effort sections keep last-good on transient failure; unified
  optical thresholds; LoginView prefill-once; populatedBuckets unique ForEach id;
  Format rounding rollover; dead-code/docstring/dedup cleanups.

Verification pending on the Mac (no Swift toolchain on the Linux dev box).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

ONUDetailView.swift

@@ -129,12 +129,14 @@ struct ONUDetailView: View {
 
     @ViewBuilder private func opticalSection(_ s: ONUStateDoc) -> some View {
         Section {
-            opticalRow("RX optical", s.rxOpticalDBm, green: -28, warn: -30)
-            opticalRow("TX optical", s.txOpticalDBm, green: 3, warn: 3)
+            opticalRow("RX optical", s.rxOpticalDBm,
+                       green: OpticalThreshold.rxGreenFloor, warn: OpticalThreshold.rxRedFloor)
+            opticalRow("TX optical", s.txOpticalDBm,
+                       green: OpticalThreshold.txGreenFloor, warn: OpticalThreshold.txGreenFloor)
         } header: {
             Text("Live optical")
         } footer: {
-            Text("Green RX ≥ −30 dBm, TX ≥ 3 dBm (user guide §7).")
+            Text("Green RX ≥ −28 dBm, TX ≥ 3 dBm (user guide §7).")
         }
         Section("FEC error counters") {
             fecRow("ONU pre-FEC",  s.onuPreFEC,  isPost: false)