Add daily notification wakeups and a make watchapp packaging target

Schedules a one-shot Pebble wakeup for the configured notification
time, re-arming it on every launch and config change, and vibrates/
refreshes the report when it fires (foreground or fresh launch).
Also adds a `make watchapp` target that builds the watchapp via the
Pebble SDK and copies a versioned .pbw to dist/, matching `make
package`'s version resolution — deliberately not wired into CI, which
has no Pebble SDK installed.

README.md

@@ -52,6 +52,13 @@ interpreter/                     Separate module + binary (dist/interpreter-cli)
                                   deck-engine's --format json output. Supports
                                   --format text|html|json and --lang en|de for
                                   its own output too (see CLAUDE.md).
+watch/                            The actual Pebble watchapp - links engine/src/
+                                  and interpreter/src/ in directly (see CLAUDE.md's
+                                  "Portability to the watch"), plus its own
+                                  persistence, reading recompute, UI, daily
+                                  notification, and config page. Built separately
+                                  from the rest of this repo (`make watchapp`,
+                                  below) - requires the Pebble SDK.
 docs/                            Architecture/dataflow diagrams, input/output format reference.
 Makefile                         Single root Makefile, builds both engine/ and
                                   interpreter/, and packages a release (`make package`).
@@ -78,6 +85,15 @@ make package  # -> dist/deck-in-a-dash-<version>-linux-<arch>.tar.gz, a
 
 Requires only a C99 compiler and `make` — no other dependencies.
 
+**Building the watch app itself** (`watch/`, the actual Pebble app)
+needs the separate Pebble SDK (`pebble` on `PATH`), so it's a separate
+target, not part of `make`/`make test`/`make package` above:
+
+```bash
+make watchapp # -> dist/deck-in-a-dash-<version>.pbw, same version
+              #    resolution as `make package`
+```
+
 ## Running
 
 **Daily use**, via `dist/run-engine.sh`: pulls today's date and the