fix(ui): F8-06 calculator polish — unified spinner UX, lock-infeasible on (0, 1), dropdown reset-changes

Owner review on PR #61:

- п.9 (option B). Hide the native spinner on EVERY numeric input in
  the calculator (DWSC blocks, armament, tech, planet MAT, custom
  load, lock value, modernization target tech) and drive every step
  through ArrowUp / ArrowDown. The column widths stay stable and the
  inputs read consistently across the whole row. The ship blocks
  keep the smart (0 ↔ 1) jump on ArrowUp/ArrowDown; armament steps
  ±1 with a JS handler instead of relying on the native spinner.
  Other inputs step by their natural grain (±0.001 for tech / lock,
  ±0.01 for MAT / load).
- п.10. Tech-level labels (`tech-val`) and the planet MAT label
  (`mat-val`) now read through the same `Ceil3` formatter as the
  derived results, so plain-text numeric values share the report's
  3-decimal tabular formatting. The design-area component receives
  `formatNumber` as a prop; the resolved (goal-seek) cell uses the
  same formatter, so the read-only computed value matches the rest
  of the row.
- п.12. `computeCalculator` now validates the back-solved block
  against the same DWSC rule the live validator enforces (`0` or
  `≥ 1`). When the solver lands in the `(0, 1)` gap (e.g. attack
  0.5 / weaponsTech 1.5 → weapons 0.333…) the lock is flagged
  infeasible — the lock input flips red and the claimed block is
  NOT back-solved into the invalid range, so the design preview
  keeps reading the user's own typed values instead of silently
  showing a sub-1 block.
- new. Selecting an existing ship class from the name datalist now
  loads it immediately. `change` fires only on blur in Firefox,
  which is why the previous behaviour looked delayed; switching the
  load to `oninput` with an `InputEvent.inputType` check makes the
  load synchronous everywhere (datalist replacement carries
  `"insertReplacementText"` in Chromium / WebKit, `undefined` in
  Firefox; keyboard typing always carries a typing `inputType`).
  Before loading we compare the live blocks to the previously
  loaded class (or to the empty defaults) and, if they differ, ask
  through a `window.confirm`. On decline we revert the name field
  and leave the design untouched.

Tests: calculator-tab and calc-model gain six cases (armament
step, tech/MAT formatter labels, lock infeasible on (0, 1) for
both attack→weapons and emptyMass→cargo, lock-value Arrow step,
dropdown immediate load + confirm-blocks-load + confirm-allows-load),
all 779 vitest tests green. docs/calculator-ux.md follows the new
behaviour.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

ui/frontend/src/lib/i18n/locales/ru.ts

@@ -424,6 +424,7 @@ const ru: Record<keyof typeof en, string> = {
 	"game.calculator.invalid.tech_below_current": "технологический уровень не может быть ниже ваших текущих технологий на этом ходу",
 	"game.calculator.invalid.load_over_capacity": "загрузка превышает грузоподъёмность корабля",
 	"game.calculator.lock.no_drive": "задайте ненулевой двигатель, прежде чем фиксировать скорость",
+	"game.calculator.confirm_reset_for_load": "Сбросить несохранённые изменения и загрузить класс «{name}»?",
 
 	"game.table.sciences.title": "науки",
 	"game.table.sciences.column.name": "название",