fix(capture): ±90° tilt slider midpoint + two-finger rotate

Clamp tape tilt to [-90, 90] so the slider knob starts centered and
CCW works. PhotoStage pinch now tracks angle as well as zoom.

frontend/src/capture/AxisPanel.svelte

@@ -1,7 +1,7 @@
 <script lang="ts">
   import type { Capture } from './capture.types';
   import type { TapeTransform } from './tapeGeometry';
-  import { defaultTicks } from './tapeGeometry';
+  import { clampTiltDeg, defaultTicks } from './tapeGeometry';
   import PhotoStage from './PhotoStage.svelte';
   import { getCropFill, setCropFill } from '../settings/cropFill';
   import { cropMarginFraction } from '../png/crop';
@@ -21,13 +21,14 @@
   const onTapeChange = (t: TapeTransform) => setTape(t);
 
   const nudgeTilt = (delta: number) => {
-    setTape({ ...tape, tiltDeg: tape.tiltDeg + delta });
+    setTape({ ...tape, tiltDeg: clampTiltDeg(tape.tiltDeg + delta) });
   };
 
   const setTilt = (deg: number) => {
-    setTape({ ...tape, tiltDeg: deg });
+    const clamped = clampTiltDeg(deg);
+    setTape({ ...tape, tiltDeg: clamped });
     // Keep legacy path warm for any callers still using setAxisAngle.
-    setAxisAngle(deg);
+    setAxisAngle(clamped);
   };
 
   const nudgeZoom = (dir: number) => {
@@ -67,14 +68,14 @@
       <div class="angle">
         <button type="button" class="thumb" aria-label="Tilt left" on:click={() => nudgeTilt(-1)}>−</button>
         <input
-          type="range" min="0" max="359" step="0.1"
-          value={((tiltShown % 360) + 360) % 360}
+          type="range" min="-90" max="90" step="0.1"
+          value={clampTiltDeg(tiltShown)}
           on:input={(e) => setTilt(Number(e.currentTarget.value))}
         />
         <button type="button" class="thumb" aria-label="Tilt right" on:click={() => nudgeTilt(1)}>+</button>
         <span class="val">{tiltShown}°</span>
       </div>
-      <p class="nudge">← → tilt 1° · Shift+← → 0.1° · or drag the ↻ handle</p>
+      <p class="nudge">±90° · ← → tilt 1° · Shift+← → 0.1° · two-finger twist · or drag the ↻ handle</p>
     </div>
 
     <div>