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.

config.py

@@ -0,0 +1,27 @@
+import os
+from pathlib import Path
+
+BASE_DIR = Path(__file__).resolve().parent
+INSTANCE_DIR = Path(os.environ.get("INSTANCE_DIR", BASE_DIR / "instance"))
+UPLOADS_DIR = INSTANCE_DIR / "uploads"
+DB_PATH = INSTANCE_DIR / "boarding_pass.db"
+
+PORT = int(os.environ.get("PORT", "8080"))
+MAX_UPLOAD_MB = int(os.environ.get("MAX_UPLOAD_MB", "15"))
+
+PUBLIC_BASE_URL = os.environ.get("PUBLIC_BASE_URL", "").rstrip("/")
+AIRTRAIL_BASE_URL = os.environ.get("AIRTRAIL_BASE_URL", "").rstrip("/")
+AIRTRAIL_API_KEY = os.environ.get("AIRTRAIL_API_KEY", "")
+
+FLIGHTAWARE_USER_AGENT = (
+    "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 "
+    "(KHTML, like Gecko) Chrome/124.0 Safari/537.36"
+)
+
+MAX_TRACK_POINTS = 2000
+MAX_FETCH_ATTEMPTS = 5
+
+
+def ensure_dirs() -> None:
+    INSTANCE_DIR.mkdir(parents=True, exist_ok=True)
+    UPLOADS_DIR.mkdir(parents=True, exist_ok=True)