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-tauri/capabilities/default.json

@@ -2,7 +2,7 @@
   "$schema": "https://raw.githubusercontent.com/nicegui-fr/nicegui/main/src-tauri/gen/schemas/desktop-schema.json",
   "identifier": "default",
   "description": "Capability for the main window",
-  "windows": ["main", "mini", "break"],
+  "windows": ["main", "mini", "break", "microbreak", "dim", "break-overlay-0", "break-overlay-1", "break-overlay-2", "break-overlay-3", "break-overlay-4", "break-overlay-5"],
   "permissions": [
     "core:window:allow-start-dragging",
     "core:window:allow-minimize",