Stage 04.1 - storage foundation (PostgreSQL) and system dashboard UI

app/src/storage/models.py

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+from __future__ import annotations
+
+from dataclasses import dataclass
+
+
+@dataclass(slots=True)
+class BalanceSnapshotRecord:
+    id: int | None
+    created_at: str
+    source: str
+    payload_json: str
+
+
+@dataclass(slots=True)
+class JournalEventRecord:
+    id: int | None
+    created_at: str
+    level: str
+    event_type: str
+    message: str
+    payload_json: str | None
+
+
+@dataclass(slots=True)
+class OrderDraftRecord:
+    id: int | None
+    created_at: str
+    symbol: str
+    side: str
+    order_type: str
+    quantity: str
+    status: str
+    payload_json: str | None

app/src/storage/schema.py

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+from __future__ import annotations
+
+from src.storage.session import get_connection
+
+
+DDL = [
+    '''
+    CREATE TABLE IF NOT EXISTS balance_snapshots (
+        id BIGSERIAL PRIMARY KEY,
+        created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+        source TEXT NOT NULL,
+        payload_json JSONB NOT NULL
+    )
+    ''',
+    '''
+    CREATE TABLE IF NOT EXISTS journal_events (
+        id BIGSERIAL PRIMARY KEY,
+        created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+        level TEXT NOT NULL,
+        event_type TEXT NOT NULL,
+        message TEXT NOT NULL,
+        payload_json JSONB
+    )
+    ''',
+    '''
+    CREATE TABLE IF NOT EXISTS order_drafts (
+        id BIGSERIAL PRIMARY KEY,
+        created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+        symbol TEXT NOT NULL,
+        side TEXT NOT NULL,
+        order_type TEXT NOT NULL,
+        quantity NUMERIC(36, 18) NOT NULL,
+        status TEXT NOT NULL,
+        payload_json JSONB
+    )
+    '''
+]
+
+
+def init_schema() -> None:
+    with get_connection() as connection:
+        with connection.cursor() as cursor:
+            for statement in DDL:
+                cursor.execute(statement)

app/src/storage/session.py

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+from __future__ import annotations
+
+from contextlib import contextmanager
+
+import psycopg
+
+from src.core.config import load_settings
+
+
+def build_dsn() -> str:
+    settings = load_settings()
+    password_part = settings.db_password.replace("@", "%40")
+    return (
+        f"postgresql://{settings.db_user}:{password_part}"
+        f"@{settings.db_host}:{settings.db_port}/{settings.db_name}"
+    )
+
+
+@contextmanager
+def get_connection():
+    connection = psycopg.connect(build_dsn(), autocommit=False)
+    try:
+        yield connection
+        connection.commit()
+    finally:
+        connection.close()
+
+
+def check_database_health() -> tuple[bool, str]:
+    try:
+        with get_connection() as connection:
+            with connection.cursor() as cursor:
+                cursor.execute("SELECT version()")
+                row = cursor.fetchone()
+                if row is None:
+                    return False, "PostgreSQL ping returned no rows."
+
+                version = str(row[0]).strip()
+    except Exception as exc:
+        return False, f"PostgreSQL error: {exc}"
+
+    return True, version