fix(wasm): make the web build actually run in the browser

With the wasm bundle building, get it rendering in a browser:

- Enable iced `webgl` so wgpu uses WebGL2 where WebGPU is absent
  (e.g. Firefox by default), and `fira-sans` so UI text has an
  embedded font (the web has no system fonts) — without it every
  label was blank.
- Replace `std::time::Instant` with `iced::time::Instant` (web-safe);
  `Instant::now()` panics ("time not implemented") on wasm and crashed
  at boot via the command line.
- Skip the batched-hatch pipeline on wasm: its bind group needs
  vertex-stage storage buffers, which WebGL2 lacks (validation error
  on "New drawing"). Fields become Option; upload/draw guard on them.
  Hatches don't draw on the web for now; everything else does.
- Fix the trunk feature flag (`data-cargo-no-default-features`) and
  ignore the `dist/` build output.

Native build + 75 tests unchanged.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Cargo.lock

@@ -6336,6 +6336,7 @@ dependencies = [
  "thiserror 2.0.18",
  "wgpu-core-deps-apple",
  "wgpu-core-deps-emscripten",
+ "wgpu-core-deps-wasm",
  "wgpu-core-deps-windows-linux-android",
  "wgpu-hal",
  "wgpu-types",
@@ -6359,6 +6360,15 @@ dependencies = [
  "wgpu-hal",
 ]
 
+[[package]]
+name = "wgpu-core-deps-wasm"
+version = "27.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9b1027dcf3b027a877e44819df7ceb0e2e98578830f8cd34cd6c3c7c2a7a50b7"
+dependencies = [
+ "wgpu-hal",
+]
+
 [[package]]
 name = "wgpu-core-deps-windows-linux-android"
 version = "27.0.0"