Make the pee/poo confetti a bottom-up fireworks fountain

Rework the effect: instead of a small burst from the tapped button, 30 emoji
launch from across the bottom of the screen, rise to random peaks while
drifting sideways, then arc back down and fade — staggered launches and varied
speed/size/rotation for a fuller, firework feel. Still pointer-events:none,
self-removing, and gated by the Settings toggle and reduced-motion.

src/changelog.json

@@ -1,5 +1,5 @@
 [
-  { "date": "2026-08-01", "text": "Logging a pee or poo now sets off a little burst of 💧/💩 confetti from the button — a tiny celebration you can switch off in Settings (and it honours a reduced-motion preference)" },
+  { "date": "2026-08-01", "text": "Logging a pee or poo now sets off 💧/💩 fireworks that shoot up from the bottom of the screen — a little celebration you can switch off in Settings (and it honours a reduced-motion preference)" },
   { "date": "2026-08-01", "text": "Tidied the header on long names and ages — the name now truncates instead of shoving the buttons, and the age reads as a compact \"16 wk · 3 mo 3 wk\"; weight-log rows are a single line again (\"Aug 1 · 16 wk\")" },
   { "date": "2026-07-26", "text": "Added a fan-chart view of the pedigree (toggle it in the header): your dog at the centre with each generation fanning outward as a ring, so many generations fit at once without the tree sprawling sideways — tap a wedge for that dog, and repeated ancestors keep their colour" },
   { "date": "2026-07-26", "text": "Added a Collapse all / Expand all toggle to the pedigree, to fold the whole tree down to your dog or open every branch at once" },