Record prices to SQLite database for historical tracking, closes #3

Stores item_number, title, size_gb, price, category, seen_at in
data/prices.db with (item_number, seen_at) as the primary key — one
row per item per day. Uses INSERT OR REPLACE so re-running for the
same day is safe. Called automatically from build().

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

crawl.py

@@ -4,6 +4,7 @@
 import collections
 import configparser
 import decimal
+import sqlite3
 import logging
 import os
 import random
@@ -333,6 +334,46 @@ def group_items(
         yield {"name": name, "label": label, "items": items}
 
 
+db_path = os.path.join(data_root, "prices.db")
+sqlite3.register_adapter(Decimal, str)
+
+
+def init_db(conn: sqlite3.Connection) -> None:
+    """Create tables if they don't exist."""
+    conn.execute("""
+        CREATE TABLE IF NOT EXISTS price (
+            item_number TEXT    NOT NULL,
+            title       TEXT    NOT NULL,
+            size_gb     NUMERIC NOT NULL,
+            price       NUMERIC NOT NULL,
+            category    TEXT    NOT NULL,
+            seen_at     DATE    NOT NULL,
+            PRIMARY KEY (item_number, seen_at)
+        )
+    """)
+    conn.commit()
+
+
+def record_prices(data: list[Grouped], today: date) -> None:
+    """Record today's prices to the database."""
+    conn = sqlite3.connect(db_path)
+    init_db(conn)
+    for cat in data:
+        for item in cat["items"]:
+            conn.execute(
+                """
+                INSERT OR REPLACE INTO price
+                    (item_number, title, size_gb, price, category, seen_at)
+                VALUES (?, ?, ?, ?, ?, ?)
+                """,
+                (item["number"], item["title"], item["size_gb"],
+                 item["price"], cat["name"], today),
+            )
+    conn.commit()
+    conn.close()
+    logger.info("prices recorded", db=db_path, date=today)
+
+
 def get_build_root() -> str:
     """Read build_dir from ~/.config/newegg-hdd/config, fall back to output/."""
     config_path = os.path.expanduser("~/.config/newegg-hdd/config")
@@ -353,6 +394,7 @@ def build() -> None:
     env = Environment(loader=FileSystemLoader(templates_dir))
 
     data = list(group_items(today))
+    record_prices(data, today)
     index = os.path.join(build_root, "index.html")
     index_template = env.get_template("index.html")
     page = index_template.render(best=data, today=today)