Add touch gesture support for emery/flint/gabbro

[brooks2564]

Summary

• Swipe up/down scrolls through forecast hours
• Tap anywhere cycles to the next data page (conditions → airflow → experiential)
• Buttons still work exactly as before — touch is purely additive
• Guarded by PBL_TOUCHSCREEN so non-touch platforms (aplite, basalt, chalk, diorite) are completely unaffected

Implementation

Navigation logic was extracted into prv_navigate_up(), prv_navigate_down(), and prv_navigate_page() helpers shared by both the button click handlers and the new touch handler. touch_service_subscribe is called in prv_window_load and unsubscribed in prv_window_unload.

Test plan

• Built clean for all 7 platforms
• Installed and tested on Pebble Time 2 (emery)
• Tap cycles pages correctly
• Swipe up/down scrolls hours correctly
• Buttons continue to work as expected

🤖 Generated with Claude Code

[erlog135]

Thanks for taking the time to make a pull request! There are some issues as is, which will need to be fixed before I would merge this:

1. There shouldn't be any .pbw files in the source. Those are usually generated in a build directory which is excluded from this project.
2. The flint platform doesn't have a touchscreen, according to the Hardware Information table.
3. Checking the platform isn't necessary for creating a custom definition of whether or not there is a touchscreen, since SDK 4.9.169 introduced a PBL_TOUCH definition. You can just query that directly.

Also, if you want to test the app locally, but don't want to bother with setting up a WeatherKit key, you can go to app/src/c/utils/demo.h and change DEMO_MODE to 1 in order to load demo data. Just remember to change it back before committing!