Feature: nutrition module (keto macros + intermittent fasting + electrolytes)

Backend:
- models/nutrition.py: NutritionGoal, Fast, ElectrolyteLog tables
- schemas/nutrition.py: Pydantic schemas for new endpoints
- routers/nutrition.py: /api/nutrition/{today,goals,fasts,electrolytes}
- main.py: register router + migration for new tables + seed keto point rules

Frontend:
- pages/Nutrition.jsx: macro bars, fast timer, eating window, electrolyte quick-add
- App.jsx: /nutrition route + Keto nav tab
- api.js: nutrition endpoints

Points schema for fasts (tier-based partial credit):
16:8=25, 18:6=40, 20:4=60, 24h=200, 36h=350, 48h=500, 72h=1000

Defaults tuned for Scot: 135kg M 44yo strict keto, 12:00-20:00 window,
Asia/Bangkok timezone, 2400/2600 cal rest/training, 20g net carb cap.

backend/app/models/__init__.py

@@ -9,6 +9,7 @@ from app.models.oauth import OAuthToken
 from app.models.resource import Resource
 from app.models.catalog import ProgramCatalog, CatalogWorkout, CrawlQueue, WorkoutLog
 from app.models.support import SupportThread, SupportMessage
+from app.models.nutrition import NutritionGoal, Fast, ElectrolyteLog
 
 __all__ = [
     "User", "UserProfile", "Program", "ActivityLog", "FoodLog",
@@ -16,4 +17,5 @@ __all__ = [
     "OAuthToken", "Resource",
     "ProgramCatalog", "CatalogWorkout", "CrawlQueue", "WorkoutLog",
     "SupportThread", "SupportMessage",
+    "NutritionGoal", "Fast", "ElectrolyteLog",
 ]