Add multi-user auth, admin panel, and timezone support; rename to Yolkbook

- Rename app from Eggtracker to Yolkbook throughout
- Add JWT-based authentication (python-jose, passlib/bcrypt)
- Add users table; all data tables gain user_id FK for full data isolation
- Super admin credentials sourced from ADMIN_USERNAME/ADMIN_PASSWORD env vars,
  synced on every startup; orphaned rows auto-assigned to admin post-migration
- Login page with self-registration; JWT stored in localStorage (30-day expiry)
- Admin panel (/admin): list users, reset passwords, disable/enable, delete,
  and impersonate (Login As) with Return to Admin banner
- Settings modal (gear icon in nav): timezone selector and change password
- Timezone stored per-user; stats date windows computed in user's timezone;
  date input setToday() respects user timezone via Intl API
- migrate_v2.sql for existing single-user installs
- Auto-migration adds timezone column to users on startup
- Updated README with full setup, auth, admin, and migration docs

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/models.py

@@ -1,13 +1,27 @@
 from datetime import date, datetime
-from sqlalchemy import Integer, Date, DateTime, Text, Numeric, func
+from sqlalchemy import Boolean, Integer, Date, DateTime, Text, Numeric, String, ForeignKey, UniqueConstraint, func
 from sqlalchemy.orm import Mapped, mapped_column
 from database import Base
 
 
+class User(Base):
+    __tablename__ = "users"
+
+    id:              Mapped[int]      = mapped_column(Integer, primary_key=True, autoincrement=True)
+    username:        Mapped[str]      = mapped_column(String(64), unique=True, nullable=False, index=True)
+    hashed_password: Mapped[str]      = mapped_column(String(255), nullable=False)
+    is_admin:        Mapped[bool]     = mapped_column(Boolean, default=False, nullable=False)
+    is_disabled:     Mapped[bool]     = mapped_column(Boolean, default=False, nullable=False)
+    timezone:        Mapped[str]      = mapped_column(String(64), nullable=False, default='UTC')
+    created_at:      Mapped[datetime] = mapped_column(DateTime, server_default=func.now())
+
+
 class EggCollection(Base):
     __tablename__ = "egg_collections"
+    __table_args__ = (UniqueConstraint("user_id", "date", name="uq_user_date"),)
 
     id:         Mapped[int]      = mapped_column(Integer, primary_key=True, autoincrement=True)
+    user_id:    Mapped[int]      = mapped_column(Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True)
     date:       Mapped[date]     = mapped_column(Date, nullable=False, index=True)
     eggs:       Mapped[int]      = mapped_column(Integer, nullable=False)
     notes:      Mapped[str]      = mapped_column(Text, nullable=True)
@@ -18,6 +32,7 @@ class FlockHistory(Base):
     __tablename__ = "flock_history"
 
     id:            Mapped[int]      = mapped_column(Integer, primary_key=True, autoincrement=True)
+    user_id:       Mapped[int]      = mapped_column(Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True)
     date:          Mapped[date]     = mapped_column(Date, nullable=False, index=True)
     chicken_count: Mapped[int]      = mapped_column(Integer, nullable=False)
     notes:         Mapped[str]      = mapped_column(Text, nullable=True)
@@ -28,6 +43,7 @@ class FeedPurchase(Base):
     __tablename__ = "feed_purchases"
 
     id:            Mapped[int]      = mapped_column(Integer, primary_key=True, autoincrement=True)
+    user_id:       Mapped[int]      = mapped_column(Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True)
     date:          Mapped[date]     = mapped_column(Date, nullable=False, index=True)
     bags:          Mapped[float]    = mapped_column(Numeric(5, 2), nullable=False)
     price_per_bag: Mapped[float]    = mapped_column(Numeric(10, 2), nullable=False)
@@ -39,6 +55,7 @@ class OtherPurchase(Base):
     __tablename__ = "other_purchases"
 
     id:         Mapped[int]      = mapped_column(Integer, primary_key=True, autoincrement=True)
+    user_id:    Mapped[int]      = mapped_column(Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True)
     date:       Mapped[date]     = mapped_column(Date, nullable=False, index=True)
     total:      Mapped[float]    = mapped_column(Numeric(10, 2), nullable=False)
     notes:      Mapped[str]      = mapped_column(Text, nullable=True)