Add pomodoro, microbreaks, breathing guide, screen dimming, presentation mode, goals, multi-monitor, and activity manager

Major feature release (v0.1.3) adding 15 new features to the break timer:

Backend (Rust):
- Pomodoro cycle tracking with configurable short/long break pattern
- Microbreak scheduling (20-20-20 rule) with independent timer
- Screen dimming events with gradual opacity progression
- Presentation mode detection (fullscreen app deferral)
- Smart break detection (natural idle breaks counting toward goals)
- Daily goal tracking and streak milestone events
- Multi-monitor break overlay support
- Working hours enforcement with per-day schedules
- Weekly summary and natural break stats queries
- Config expanded to 71 validated fields

Frontend (Svelte):
- 6 new components: BreathingGuide, ActivityManager, BreakOverlay,
  MicrobreakOverlay, DimOverlay, Celebration
- Breathing guide with 5 patterns and animated pulsing halo
- Activity manager with favorites, custom activities, momentum scroll
- Confetti celebrations on milestones and goal completion
- Dashboard indicators (pomodoro/microbreak/goal) moved inside ring
- Settings reorganized into 18 logical cards
- Breathing pattern selector redesigned with timing descriptions
- Break activities expanded from 40 to 71 curated exercises
- Sound presets expanded from 4 to 8
- Stats view with weekly summary and natural break tracking

Also: version bump to 0.1.3, CHANGELOG, README and CLAUDE.md updates

src/lib/utils/activities.ts

@@ -106,10 +106,55 @@ export function getCategoryLabel(cat: BreakActivity["category"]): string {
   return categoryLabels[cat];
 }
 
-/** Pick a random activity, optionally excluding a previous one */
-export function pickRandomActivity(exclude?: BreakActivity): BreakActivity {
-  const pool = exclude
-    ? breakActivities.filter((a) => a.text !== exclude.text)
-    : breakActivities;
-  return pool[Math.floor(Math.random() * pool.length)];
+/** Pick a random activity, optionally excluding a previous one.
+ *  When config is provided, respects disabled/favorite/custom activity settings. */
+export function pickRandomActivity(
+  exclude?: BreakActivity,
+  config?: {
+    disabled_builtin_activities?: string[];
+    favorite_builtin_activities?: string[];
+    custom_activities?: Array<{ category: string; text: string; is_favorite: boolean; enabled: boolean }>;
+    favorite_weight?: number;
+  },
+): BreakActivity {
+  const disabled = new Set(config?.disabled_builtin_activities ?? []);
+  const favorites = new Set(config?.favorite_builtin_activities ?? []);
+  const weight = config?.favorite_weight ?? 3;
+
+  // Build pool: enabled builtins + enabled customs
+  let pool: BreakActivity[] = breakActivities.filter((a) => !disabled.has(a.text));
+
+  // Add enabled custom activities
+  if (config?.custom_activities) {
+    for (const ca of config.custom_activities) {
+      if (ca.enabled) {
+        const cat = (["eyes", "stretch", "breathing", "movement"].includes(ca.category)
+          ? ca.category
+          : "movement") as BreakActivity["category"];
+        pool.push({ category: cat, text: ca.text });
+      }
+    }
+  }
+
+  // Exclude previous
+  if (exclude) {
+    pool = pool.filter((a) => a.text !== exclude.text);
+  }
+
+  if (pool.length === 0) {
+    return exclude ?? breakActivities[0];
+  }
+
+  // Build weighted pool: favorites appear `weight` times
+  const weighted: BreakActivity[] = [];
+  for (const a of pool) {
+    const isFav = favorites.has(a.text) ||
+      (config?.custom_activities?.some((c) => c.text === a.text && c.is_favorite) ?? false);
+    const count = isFav ? weight : 1;
+    for (let i = 0; i < count; i++) {
+      weighted.push(a);
+    }
+  }
+
+  return weighted[Math.floor(Math.random() * weighted.length)];
 }