add paper trading: mark a setup as taken, track open P&L, sell

New paper_trades table (migration 007) + service/router. "Mark as taken" on each
setup card (shares prefilled from position sizing, entry from current price, both
editable) records a simulated trade. Overview gains an Open Trades table that
marks each position to the latest close — P&L in $, %, and R-multiples — with a
total unrealized P&L footer and a Sell button to close at the current price.
Closed trades are retained for future realized-P&L reporting.

Deploy: alembic upgrade (new paper_trades table).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

alembic/versions/007_add_paper_trades.py

@@ -0,0 +1,45 @@
+"""add paper_trades table
+
+Revision ID: 007
+Revises: 006
+Create Date: 2026-06-16 00:00:00.000000
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = "007"
+down_revision: Union[str, None] = "006"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        "paper_trades",
+        sa.Column("id", sa.Integer(), nullable=False),
+        sa.Column("user_id", sa.Integer(), nullable=False),
+        sa.Column("ticker_id", sa.Integer(), nullable=False),
+        sa.Column("direction", sa.String(length=10), nullable=False),
+        sa.Column("entry_price", sa.Float(), nullable=False),
+        sa.Column("shares", sa.Float(), nullable=False),
+        sa.Column("stop_loss", sa.Float(), nullable=False),
+        sa.Column("target", sa.Float(), nullable=False),
+        sa.Column("status", sa.String(length=10), nullable=False),
+        sa.Column("opened_at", sa.DateTime(timezone=True), nullable=False),
+        sa.Column("close_price", sa.Float(), nullable=True),
+        sa.Column("closed_at", sa.DateTime(timezone=True), nullable=True),
+        sa.ForeignKeyConstraint(["user_id"], ["users.id"], ondelete="CASCADE"),
+        sa.ForeignKeyConstraint(["ticker_id"], ["tickers.id"], ondelete="CASCADE"),
+        sa.PrimaryKeyConstraint("id"),
+    )
+    op.create_index("ix_paper_trades_user_status", "paper_trades", ["user_id", "status"])
+
+
+def downgrade() -> None:
+    op.drop_index("ix_paper_trades_user_status", table_name="paper_trades")
+    op.drop_table("paper_trades")