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>

tests/circuit.controller.test.ts

@@ -0,0 +1,100 @@
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+import { getNextCircuitIdentifier } from "../src/server/controllers/circuit.controller.js";
+import {
+  circuitListRepository,
+  circuitSectionRepository,
+} from "../src/server/composition/application-repositories.js";
+import { circuitNumberingService } from "../src/server/composition/circuit-numbering-service.js";
+
+function createMockResponse() {
+  let statusCode = 200;
+  let body: unknown;
+  return {
+    response: {
+      status(code: number) {
+        statusCode = code;
+        return this;
+      },
+      json(value: unknown) {
+        body = value;
+        return this;
+      },
+    },
+    getStatusCode: () => statusCode,
+    getBody: () => body,
+  };
+}
+
+describe("circuit controller", () => {
+  it("returns the next identifier when the section belongs to the project", async () => {
+    const originals = {
+      findSection: circuitSectionRepository.findById,
+      findList: circuitListRepository.findById,
+      getNextIdentifier: circuitNumberingService.getNextIdentifier,
+    };
+    circuitSectionRepository.findById = async () =>
+      ({ id: "section-1", circuitListId: "list-1", prefix: "-1F" }) as never;
+    circuitListRepository.findById = async (projectId: string, circuitListId: string) =>
+      projectId === "project-1" && circuitListId === "list-1"
+        ? ({ id: "list-1", projectId: "project-1" } as never)
+        : null;
+    circuitNumberingService.getNextIdentifier = async () => "-1F3";
+    const mock = createMockResponse();
+    try {
+      await getNextCircuitIdentifier(
+        { params: { projectId: "project-1", sectionId: "section-1" } } as never,
+        mock.response as never
+      );
+    } finally {
+      circuitSectionRepository.findById = originals.findSection;
+      circuitListRepository.findById = originals.findList;
+      circuitNumberingService.getNextIdentifier = originals.getNextIdentifier;
+    }
+    assert.deepEqual(mock.getBody(), {
+      sectionId: "section-1",
+      nextIdentifier: "-1F3",
+    });
+  });
+
+  it("returns 404 instead of leaking numbering state for a section from another project", async () => {
+    const originals = {
+      findSection: circuitSectionRepository.findById,
+      findList: circuitListRepository.findById,
+    };
+    circuitSectionRepository.findById = async () =>
+      ({ id: "section-1", circuitListId: "list-1", prefix: "-1F" }) as never;
+    // The section exists, but its circuit list does not belong to the requesting project.
+    circuitListRepository.findById = async () => null;
+    const mock = createMockResponse();
+    try {
+      await getNextCircuitIdentifier(
+        { params: { projectId: "foreign-project", sectionId: "section-1" } } as never,
+        mock.response as never
+      );
+    } finally {
+      circuitSectionRepository.findById = originals.findSection;
+      circuitListRepository.findById = originals.findList;
+    }
+    assert.equal(mock.getStatusCode(), 404);
+    assert.deepEqual(mock.getBody(), { error: "Section not found" });
+  });
+
+  it("returns 404 for a section that does not exist", async () => {
+    const originals = {
+      findSection: circuitSectionRepository.findById,
+    };
+    circuitSectionRepository.findById = async () => null;
+    const mock = createMockResponse();
+    try {
+      await getNextCircuitIdentifier(
+        { params: { projectId: "project-1", sectionId: "missing" } } as never,
+        mock.response as never
+      );
+    } finally {
+      circuitSectionRepository.findById = originals.findSection;
+    }
+    assert.equal(mock.getStatusCode(), 404);
+    assert.deepEqual(mock.getBody(), { error: "Section not found" });
+  });
+});