feat: add period tracker with calendar, predictions, fertility tracking, and sharing

Full period tracking system for the fitness measure page:
- Period logging with start/end dates, edit/delete support
- EMA-based cycle and period length predictions (α=0.3, 12 future cycles)
- Calendar view with connected range strips, overflow days, today marker
- Fertility window, peak fertility, ovulation, and luteal phase visualization
- Period sharing between users with profile picture avatars
- Cycle/period stats with 95% CI below calendar
- Redesigned profile card as inline header metadata with Venus/Mars icons
- Collapsible weight and period history sections
- Full DE/EN i18n support

CLAUDE.md

@@ -85,7 +85,6 @@ When committing, bump version numbers as appropriate using semver:
 - **minor** (x.Y.0): new features, significant UI changes, new pages/routes
 - **major** (X.0.0): breaking changes, major redesigns, data model changes
 
-Version files to update (keep in sync):
-- `package.json` — site version
-- `src-tauri/tauri.conf.json` — Tauri/Android app version
-- `src-tauri/Cargo.toml` — Rust crate version
+Version files to update:
+- `package.json` — site version (bump on every commit)
+- `src-tauri/tauri.conf.json` + `src-tauri/Cargo.toml` — Tauri/Android app version. Only bump these when the Tauri app codebase itself changes (e.g. `src-tauri/` files), NOT for website-only changes.