fix(ui): calculator polish — smart input steps, unified tech/MAT lock idiom, tech floor, speed-lock ceiling fix

- pkg/calc: DriveForSpeed treats restMass==0 as a valid ceiling-only
  case (every positive drive solves it), so locking the displayed
  speed of a D=1, W=A=S=C=0 ship is no longer a phantom "infeasible".
- ship-design-area: drive/weapons/shields/cargo inputs use a JS-driven
  smart step on ArrowUp/ArrowDown (0↔1 jump, otherwise ±0.1) and hide
  the native spinner so it cannot produce invalid (0, 1) values;
  armament keeps its native step 1.
- Tech and planet MAT cells follow the same lock idiom as goal-seek
  locks: open padlock (🔓) over the inherited value → click to open
  an input with a closed padlock (🔒). The padlock slot is always
  reserved, so the column width is stable.
- Tech overrides (design area and modernization target) are floored
  at the player's current tech on this turn — a lower value is
  flagged as invalid.

ui/frontend/tests/e2e/game-shell-inspector.spec.ts

@@ -275,6 +275,9 @@ test("calculator draws reach circles for the selected planet", async ({
 	await calc.getByTestId("calculator-block-drive").fill("10");
 	await calc.getByTestId("calculator-block-shields").fill("5");
 	await calc.getByTestId("calculator-block-cargo").fill("5");
+	// Tech defaults render as a number + open lock; click to reveal the
+	// input before typing an override (the F8-06 unified lock idiom).
+	await calc.getByTestId("calculator-tech-override-drive").click();
 	await calc.getByTestId("calculator-tech-drive").fill("1.2");
 
 	await expect.poll(() => countReachCircles(page)).toBeGreaterThan(0);