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-device-row-project-command.model.ts

@@ -144,6 +144,9 @@ function assertCircuitDeviceRowUpdateFieldValue(
     if (typeof value !== "number" || !Number.isFinite(value) || value < 0) {
       throw new Error(`${field} must be a non-negative finite number.`);
     }
+    if (field === "simultaneityFactor" && value > 1) {
+      throw new Error("simultaneityFactor must not exceed 1.");
+    }
     return;
   }
   if (field === "cosPhi") {

src/domain/models/circuit-device-row-structure-project-command.model.ts

@@ -134,6 +134,9 @@ export function assertCircuitDeviceRowInsertProjectCommand(
     row.simultaneityFactor,
     "row.simultaneityFactor"
   );
+  if (row.simultaneityFactor > 1) {
+    throw new Error("row.simultaneityFactor must not exceed 1.");
+  }
   if (row.cosPhi !== null) {
     assertFiniteNumber(row.cosPhi, "row.cosPhi");
     if (row.cosPhi <= 0) {

src/domain/models/circuit-device-row.model.ts

@@ -1,24 +0,0 @@
-export interface CircuitDeviceRow {
-  id: string;
-  circuitId: string;
-  linkedProjectDeviceId?: string;
-  sortOrder: number;
-  name: string;
-  displayName: string;
-  phaseType?: string;
-  connectionKind?: string;
-  costGroup?: string;
-  category?: string;
-  level?: string;
-  roomId?: string;
-  roomNumberSnapshot?: string;
-  roomNameSnapshot?: string;
-  quantity: number;
-  manualQuantity: number;
-  powerPerUnit: number;
-  simultaneityFactor: number;
-  cosPhi?: number;
-  remark?: string;
-  overriddenFields?: string;
-}
-

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 ||

src/domain/models/circuit-section.model.ts

@@ -1,9 +0,0 @@
-export interface CircuitSection {
-  id: string;
-  circuitListId: string;
-  key: string;
-  displayName: string;
-  prefix: string;
-  sortOrder: number;
-}
-

src/domain/models/circuit.model.ts

@@ -1,19 +0,0 @@
-export interface Circuit {
-  id: string;
-  circuitListId: string;
-  sectionId: string;
-  equipmentIdentifier: string;
-  displayName?: string;
-  sortOrder: number;
-  cableType?: string;
-  cableCrossSection?: string;
-  cableLength?: number;
-  rcdAssignment?: string;
-  terminalDesignation?: string;
-  voltage?: number;
-  controlRequirement?: string;
-  status?: string;
-  isReserve: boolean;
-  remark?: string;
-}
-

src/domain/models/project-state-snapshot.model.ts

@@ -130,7 +130,7 @@ const circuitDeviceRowSchema = z.preprocess(
     quantity: finiteNumberSchema.nonnegative(),
     manualQuantity: finiteNumberSchema.nonnegative(),
     powerPerUnit: finiteNumberSchema.nonnegative(),
-    simultaneityFactor: finiteNumberSchema.nonnegative(),
+    simultaneityFactor: finiteNumberSchema.min(0).max(1),
     cosPhi: finiteNumberSchema.positive().nullable(),
     remark: nullableStringSchema,
     overriddenFields: nullableStringSchema,