Add recurring transaction detection, subscriptions page, and UK tax reporting

- Recurring service: auto-detects direct debits/subscriptions from CSV imports
  using frequency analysis; manual toggle in transaction detail drawer
- Subscriptions page (/subscriptions): groups recurring payments with monthly
  cost equivalents, next-payment badges, and re-scan trigger
- UK Tax page (/tax): payslips/P60 entry, income tax + NI + CGT + dividend tax
  calculations, configurable rate tables per tax year (pre-seeded 2024/25 and
  2025/26), editable in-app so Budget changes need no rebuild
- Migration 0006: tax_rate_configs, tax_profiles, payslips, manual_cgt_disposals
  with RLS; seeds 2025/2026 rate configs for existing users
- Chart tooltip fix: all Recharts tooltips now use TOOLTIP_STYLE constant so
  they render correctly across all dark/light themes

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

backend/app/db/models/tax.py

@@ -0,0 +1,74 @@
+import uuid
+from datetime import date, datetime
+from decimal import Decimal
+
+from sqlalchemy import Boolean, Date, DateTime, ForeignKey, Integer, LargeBinary, Numeric, SmallInteger, String, UniqueConstraint
+from sqlalchemy.dialects.postgresql import JSONB, UUID
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from app.db.base import Base
+
+
+class TaxRateConfig(Base):
+    __tablename__ = "tax_rate_configs"
+    __table_args__ = (
+        UniqueConstraint("user_id", "tax_year", "rate_type", name="uq_tax_rate_configs_user_year_type"),
+    )
+
+    id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
+    user_id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True)
+    tax_year: Mapped[int] = mapped_column(Integer, nullable=False)
+    rate_type: Mapped[str] = mapped_column(String(30), nullable=False)  # income_tax|ni|cgt|dividend
+    config: Mapped[dict] = mapped_column(JSONB, nullable=False)
+    updated_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), nullable=False)
+
+
+class TaxProfile(Base):
+    __tablename__ = "tax_profiles"
+    __table_args__ = (
+        UniqueConstraint("user_id", "tax_year", name="uq_tax_profiles_user_year"),
+    )
+
+    id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
+    user_id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True)
+    tax_year: Mapped[int] = mapped_column(Integer, nullable=False)
+    employer_name_enc: Mapped[bytes | None] = mapped_column(LargeBinary, nullable=True)
+    tax_code: Mapped[str] = mapped_column(String(20), nullable=False, default="1257L")
+    is_cumulative: Mapped[bool] = mapped_column(Boolean, nullable=False, default=True)
+    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), nullable=False)
+    updated_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), nullable=False)
+
+    payslips: Mapped[list["Payslip"]] = relationship(back_populates="tax_profile", lazy="noload")
+
+
+class Payslip(Base):
+    __tablename__ = "payslips"
+
+    id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
+    user_id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True)
+    tax_profile_id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), ForeignKey("tax_profiles.id", ondelete="CASCADE"), nullable=False, index=True)
+    period_month: Mapped[int | None] = mapped_column(SmallInteger, nullable=True)
+    period_year: Mapped[int] = mapped_column(SmallInteger, nullable=False)
+    gross_pay: Mapped[Decimal] = mapped_column(Numeric(14, 2), nullable=False)
+    income_tax_withheld: Mapped[Decimal] = mapped_column(Numeric(14, 2), nullable=False)
+    ni_withheld: Mapped[Decimal] = mapped_column(Numeric(14, 2), nullable=False)
+    net_pay: Mapped[Decimal] = mapped_column(Numeric(14, 2), nullable=False)
+    is_p60: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
+    notes_enc: Mapped[bytes | None] = mapped_column(LargeBinary, nullable=True)
+    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), nullable=False)
+
+    tax_profile: Mapped["TaxProfile"] = relationship(back_populates="payslips", lazy="noload")
+
+
+class ManualCGTDisposal(Base):
+    __tablename__ = "manual_cgt_disposals"
+
+    id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
+    user_id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True)
+    tax_year: Mapped[int] = mapped_column(Integer, nullable=False)
+    disposal_date: Mapped[date] = mapped_column(Date, nullable=False)
+    asset_description_enc: Mapped[bytes] = mapped_column(LargeBinary, nullable=False)
+    proceeds: Mapped[Decimal] = mapped_column(Numeric(14, 2), nullable=False)
+    cost_basis: Mapped[Decimal] = mapped_column(Numeric(14, 2), nullable=False)
+    notes_enc: Mapped[bytes | None] = mapped_column(LargeBinary, nullable=True)
+    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), nullable=False)