Docs: rewrite README with clear Docker and Docker Compose instructions; refactor app into package (auth, admin, pages, db); keep single entrypoint app.py

app/db.py

@@ -0,0 +1,50 @@
+import sqlite3
+from datetime import datetime
+from flask import g, current_app
+
+
+def get_db():
+    if "db" not in g:
+        g.db = sqlite3.connect(current_app.config["DATABASE"])  # type: ignore[attr-defined]
+        g.db.row_factory = sqlite3.Row
+    return g.db
+
+
+def close_db(_=None):
+    db = g.pop("db", None)
+    if db is not None:
+        db.close()
+
+
+def init_db():
+    db = get_db()
+    db.execute(
+        """
+        CREATE TABLE IF NOT EXISTS pages (
+            id INTEGER PRIMARY KEY AUTOINCREMENT,
+            uuid TEXT NOT NULL UNIQUE,
+            title TEXT NOT NULL DEFAULT '',
+            html TEXT NOT NULL,
+            created_at TEXT NOT NULL
+        );
+        """
+    )
+    # Migrate: ensure title exists
+    try:
+        cols = {row[1] for row in db.execute("PRAGMA table_info(pages)").fetchall()}
+        if "title" not in cols:
+            db.execute("ALTER TABLE pages ADD COLUMN title TEXT NOT NULL DEFAULT ''")
+    except Exception:
+        pass
+    db.commit()
+
+
+def init_app(app):
+    @app.before_request
+    def _before_request():  # noqa: D401
+        init_db()
+
+    @app.teardown_appcontext
+    def _teardown(_=None):  # noqa: D401
+        close_db()
+