Add Sud New/Load/Save and Start/Stop to the browser client

Ports on_action_sud_new/_save/_load() and on_action_sud_start/_stop()
from client/brewpi_gui.py: Load/Save stand in for the native file
dialogs with <input type="file">/FileReader and a Blob/<a download>,
New sends the same hardcoded empty-doc Load, and Start/Stop are gated
by updateSudActions() mirroring update_sud_actions()'s enabled/disabled
logic. Also fixes the status line's step number being one below what
the Progress tab's plates show for the same step (same bug just fixed
in the desktop client).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0189FkmyJkY77HqsNomr1DwV

web/TODO.md

@@ -6,15 +6,13 @@ Everything below is what that v1 pass deliberately left out - either
 flagged as deferred in the plan, or only noticed once the port was done
 and checked against the Qt source side by side.
 
-- [ ] **No way to actually run a brew.** There's no Start/Pause/Stop/
-  Confirm anywhere in `web/index.html` - `on_action_sud_start()`/
-  `on_action_sud_pause()`/`on_action_sud_stop()` (`client/brewpi_gui.py:
-  868-875`) are one-line `{"Sud": {"Start"/"Pause"/"Stop": true}}` sends,
-  trivial to add as buttons; `{"Sud": {"Confirm": true}}` already needs
+- [x] **No way to actually run a brew.** ~~There's no Start/Pause/Stop/
+  Confirm anywhere in `web/index.html`~~ Start/Stop are now wired up
+  (`btn-sud-start`/`btn-sud-stop` in `app.js`, gated by `updateSudActions()`
+  mirroring `update_sud_actions()`'s enabled/disabled logic). Still
+  missing: Pause, and `{"Sud": {"Confirm": true}}` - that one needs
   `sudUserMessage`/`sudState` (next item) to know *when* it's actually
-  waiting on one. Until this exists, the Progress tab can only watch a
-  run started from the desktop GUI (or a raw `Sud.Start` send from the
-  browser console) - it's read-only.
+  waiting on one.
 
 - [ ] **`WAIT_USER` never surfaces to the user.** `sudUserMessage` is
   tracked in `app.js` but nothing ever shows it - `show_user_message()`
@@ -26,14 +24,12 @@ and checked against the Qt source side by side.
   the `WAIT_USER` transition) plus a modal (a plain `<dialog>` works,
   no library needed) that sends `Confirm` on close.
 
-- [ ] **No schedule management.** Matches README.md's "Browser client"
-  section, called out there as deliberately deferred rather than missing
-  by oversight - `on_action_sud_new/_save/_load()`
-  (`client/brewpi_gui.py:884-912`) use native file dialogs `web/` has no
-  equivalent of yet. Load maps to `<input type="file">` +
-  `FileReader`+`{"Sud": {"Load": ...}}`; Save to a `Blob`+`<a download>`
-  of whatever the next `Json` push contains; New is just the same
-  hardcoded empty-doc `Load` Qt sends, no dialog needed at all.
+- [x] **No schedule management.** New/Load/Save are now wired up in
+  `app.js`: Load is `<input type="file">` + `FileReader` +
+  `{"Sud": {"Load": ...}}`; Save sends `{"Sud": {"Save": true}}` and
+  downloads (`Blob`+`<a download>`) whichever `Json` push answers it
+  (tracked via `sudSavePending`, mirroring `brewpi_gui.py`'s
+  `sud_save_path`); New sends the same hardcoded empty-doc `Load` Qt does.
 
 - [ ] **No temperature-controller state/cooldown indicator.** Qt shows
   the raw FSM state (`label_state.setText(msg['State'])` - e.g.