chore: unify name to "Meeting Mixer", README tech stack, name magic numbers (#16)

- Canonical name "Meeting Mixer" everywhere: <title>, README, .vch-description
  (now non-technical per convention) and package.json (meeting-mixer).
- README gains a Tech-Stack section and an accurate, non-misleading port note.
- Magic numbers replaced by named constants: LOW_PRIORITY_PENALTY in
  algorithm.js; MIN/MAX_MODERATORS_PER_DAY in utils.js, used by data.js,
  calendar.js and app.js.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

js/app.js

@@ -2,6 +2,7 @@ import { renderEmployees } from './employees.js';
 import { renderCalendar } from './calendar.js';
 import { renderDataTab } from './history.js';
 import { normalizeEmployees } from './data.js';
+import { MIN_MODERATORS_PER_DAY, MAX_MODERATORS_PER_DAY } from './utils.js';
 
 const STORAGE_KEY = 'morning-planner-state';
 
@@ -22,7 +23,8 @@ try {
     if (parsed.calendar) state.calendar = parsed.calendar;
     if (Array.isArray(parsed.history)) state.history = parsed.history;
     if (parsed.settings && Number.isInteger(parsed.settings.moderatorsPerDay)
-        && parsed.settings.moderatorsPerDay >= 1 && parsed.settings.moderatorsPerDay <= 5) {
+        && parsed.settings.moderatorsPerDay >= MIN_MODERATORS_PER_DAY
+        && parsed.settings.moderatorsPerDay <= MAX_MODERATORS_PER_DAY) {
       state.settings = { moderatorsPerDay: parsed.settings.moderatorsPerDay };
     }
   }