Fix hyperhdrAdjust: use "brightness", not "scaleOutput"

Tested against a real HyperHDR instance rather than trusting the
schema further. scaleOutput (from the current schema-adjustment.json)
produced no visible change and no trace in serverinfo's echoed-back
adjustment state. brightness (0-100, absent from that same schema)
round-tripped correctly through serverinfo and visibly dimmed real
LEDs -- confirmed live, with piccap as the sole colour source and
only this sink's JSON-RPC calls changing anything.

A schema documents what a command accepts; it does not guarantee
what a given build actually does with each field, and this is a
mismatch between HyperHDR's current dev-branch schema and whatever
build the target instance is actually running. Switched the sink to
brightness (int 0-100) throughout: wire format, config defaults
(minBrightness/maxBrightness, 20-100), status fields, and the reset
sent on close. Renamed the frontend fields and mock to match.
Cross-compiles clean. Bumped to 1.0.4.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

frontend/js/app.js

@@ -401,12 +401,12 @@
         ],
       },
       {
-        path: 'hyperhdrAdjust.minScale', label: 'Minimum brightness', type: 'number',
-        hint: '1.0 is HyperHDR\'s normal brightness. Below that dims during quiet parts.',
+        path: 'hyperhdrAdjust.minBrightness', label: 'Minimum brightness', type: 'number',
+        hint: '0-100. Applied during quiet parts. 100 is HyperHDR\'s normal brightness.',
       },
       {
-        path: 'hyperhdrAdjust.maxScale', label: 'Maximum brightness', type: 'number',
-        hint: 'Above 1.0 boosts past normal on loud peaks. HyperHDR accepts up to 2.0.',
+        path: 'hyperhdrAdjust.maxBrightness', label: 'Maximum brightness', type: 'number',
+        hint: '0-100. Applied at full level. HyperHDR does not go above 100.',
       },
     ],