Fix code-review findings across domain, persistence, server and frontend

Full-codebase review turned up five real correctness/security bugs and
a dozen smaller inconsistencies; all are fixed here with matching test
coverage:

- BMK uniqueness silently allowed German-umlaut duplicates ("Ä1" vs
  "ä1") because the DB's normalized index only folds ASCII case. Added
  a shared Unicode-aware pre-check used by every circuit/component
  insert and rename path (one of which had no pre-check at all).
- CircuitDeviceRow.simultaneityFactor had no upper bound at the row
  level (command model and snapshot/restore schema), unlike every
  sibling entity, letting a bad value silently corrupt power totals.
- Grid cell editing silently misread German thousands-separator input
  ("1.500" parsed as 1.5); "." is now rejected outright with a clear
  message instead of guessing.
- The editor's shared command runner (runCommand/applyHistory) had no
  re-entrancy guard, so a double click/drop could fire the same
  command twice and race a BMK collision or revision conflict. Added a
  synchronous ref guard plus isSaving on the buttons that lacked it.
- GET .../next-identifier leaked circuit-numbering state for sections
  in other projects (no ownership check, 400 instead of 404). Moved
  under /projects/:projectId and scoped it.

Also: added the missing circuits.section_id / circuit_device_rows.
circuit_id indexes (migration 0006), gave FormModal a focus trap /
Escape-to-close / focus restore and rebuilt ProjectSettingsModal on
top of it instead of duplicated markup, removed dead code (3 orphaned
domain model files, an unused persistence helper, a wrapper only used
by its own test), pointed the project page at GET /projects/:id
instead of listing+filtering client-side, closed the gap between the
documented 18 MB CSV limit and the ~17.17 MiB actually enforced, added
missing upper bounds on several free-text fields, filled in nine
missing German labels in the revision timeline, replaced a
key-order-fragile JSON.stringify equality check with a real field
comparison, made an implicit sort-order assumption in three
renumbering helpers explicit, cleared the sidebar's target selection
when it no longer resolves after a tree reload, and fixed
updateGlobalDevice to check-then-write instead of write-then-check.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/domain/models/circuit-protection-project-command.model.ts

@@ -71,15 +71,33 @@ export function assertCircuitProtectionUpdateProjectCommand(
   if (target !== null) {
     assertCircuitProtectionSnapshot(target, circuitId);
   }
-  if (JSON.stringify(expected) === JSON.stringify(target)) {
+  if (circuitProtectionSnapshotsEqual(expected, target)) {
     throw new Error("Circuit protection update must change state.");
   }
 }
 
+function circuitProtectionSnapshotsEqual(
+  left: CircuitProtectionSnapshot | null,
+  right: CircuitProtectionSnapshot | null
+): boolean {
+  if (left === null || right === null) {
+    return left === right;
+  }
+  return (
+    left.circuitId === right.circuitId &&
+    left.type === right.type &&
+    left.ratedCurrentA === right.ratedCurrentA &&
+    left.fuseUtilizationCategory === right.fuseUtilizationCategory &&
+    left.tripCharacteristic === right.tripCharacteristic &&
+    left.rcdType === right.rcdType &&
+    left.ratedResidualCurrentMa === right.ratedResidualCurrentMa
+  );
+}
+
 export function assertCircuitProtectionSnapshot(
   value: unknown,
   circuitId: string
-) {
+): asserts value is CircuitProtectionSnapshot {
   if (
     !isPlainObject(value) ||
     Object.keys(value).length !== 7 ||