Initial commit: boarding pass to AirTrail pipeline

Photograph/screenshot a boarding pass, decode its BCBP barcode (PDF417/
Aztec/QR/DataMatrix), fetch the historical flight track from FlightAware
the day after the flight, stage it for review, and write it into AirTrail
via its REST API on approval. ntfy notifications carry signed
Approve/Deny/Investigate actions.

db.py

@@ -0,0 +1,73 @@
+import sqlite3
+from contextlib import contextmanager
+
+import config
+
+SCHEMA = """
+CREATE TABLE IF NOT EXISTS pending_flights (
+    id                      INTEGER PRIMARY KEY AUTOINCREMENT,
+    created_at              TEXT NOT NULL,
+    updated_at              TEXT NOT NULL,
+    status                  TEXT NOT NULL DEFAULT 'queued'
+                            CHECK (status IN ('queued','pending_review','track_unavailable',
+                                               'approved','rejected','decode_failed')),
+    image_path              TEXT NOT NULL,
+    raw_bcbp                TEXT,
+    passenger_name          TEXT,
+    pnr                     TEXT,
+    from_iata               TEXT,
+    to_iata                 TEXT,
+    from_icao               TEXT,
+    to_icao                 TEXT,
+    operating_carrier_iata  TEXT,
+    operating_carrier_icao  TEXT,
+    flight_number           TEXT,
+    julian_day              INTEGER,
+    flight_date             TEXT,
+    known_departure_time    TEXT,
+    compartment             TEXT,
+    seat                    TEXT,
+    process_after           TEXT,
+    fetch_attempts          INTEGER NOT NULL DEFAULT 0,
+    track_coordinates       TEXT,
+    track_times             TEXT,
+    track_point_count       INTEGER,
+    flightaware_url         TEXT,
+    airtrail_flight_id      INTEGER,
+    parse_warnings          TEXT,
+    error_message           TEXT,
+    reviewed_at             TEXT,
+    approved_at             TEXT
+);
+CREATE INDEX IF NOT EXISTS idx_pending_flights_status_process_after
+    ON pending_flights(status, process_after);
+
+CREATE TABLE IF NOT EXISTS settings (
+    key   TEXT PRIMARY KEY,
+    value TEXT
+);
+"""
+
+
+def get_connection() -> sqlite3.Connection:
+    config.ensure_dirs()
+    conn = sqlite3.connect(config.DB_PATH, timeout=30)
+    conn.row_factory = sqlite3.Row
+    conn.execute("PRAGMA journal_mode=WAL")
+    conn.execute("PRAGMA foreign_keys=ON")
+    return conn
+
+
+@contextmanager
+def connect():
+    conn = get_connection()
+    try:
+        yield conn
+        conn.commit()
+    finally:
+        conn.close()
+
+
+def init_db() -> None:
+    with connect() as conn:
+        conn.executescript(SCHEMA)