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-grid-projection.test.ts

@@ -1,7 +1,6 @@
 import assert from "node:assert/strict";
 import { describe, it } from "node:test";
 import {
-  buildVisibleGridRows,
   buildVisibleGridRowsWithStructure,
   filterAndSortCircuitSections,
   getDistinctFilterValues,
@@ -101,7 +100,7 @@ describe("circuit grid projection", () => {
     ];
 
     const projectedSections = filterAndSortCircuitSections(emptySections, {}, null);
-    const rows = buildVisibleGridRows(projectedSections);
+    const rows = buildVisibleGridRowsWithStructure(projectedSections, { headerComponents: [], footerComponents: [] });
 
     assert.equal(projectedSections.length, 2);
     assert.deepEqual(
@@ -150,7 +149,7 @@ describe("circuit grid projection", () => {
   });
 
   it("builds the compact, grouped, reserve and placeholder row shapes", () => {
-    const rows = buildVisibleGridRows(sections);
+    const rows = buildVisibleGridRowsWithStructure(sections, { headerComponents: [], footerComponents: [] });
 
     assert.deepEqual(rows.map((row) => row.rowType), [
       "section",
@@ -191,7 +190,7 @@ describe("circuit grid projection", () => {
         },
       })),
     }));
-    const rows = buildVisibleGridRows(protectedSections);
+    const rows = buildVisibleGridRowsWithStructure(protectedSections, { headerComponents: [], footerComponents: [] });
     const protectionValue = (rowType: string) =>
       rows
         .find((row) => row.rowType === rowType)