fix(google_flights): serve airline logos from local gstatic assets

[Lxr-max]

Summary

Reviewer takeover for #22 (Google Flights airline logos) on Lxr-max/WebHarbor. Stale author PR: #23.

#23 only retargeted seed_data.py from .svg to .png. That does not fix the published seed DB (126k rows still store /static/images/airlines/<slug>.svg), and the paired HF discussion #11 is a logos-only google_flights.tar.gz (~48 KB) that must not replace the full site archive.

This PR follows the same code-side fallback as ESPN #132:

• Commit the 23 Google Flights gstatic 70px PNGs (/flights/airline_logos/70px/{IATA}.png) under sites/google_flights/static/icons/airlines/ (git-tracked, not HF-managed).
• Resolve <img> URLs at render time so templates never request a missing file and never onerror-hide a broken image.
• Prefer the committed IATA PNG over the published letter-tile SVGs; fall back to the on-disk DB path only when no PNG exists.
• Point future seed_data.py rows at /static/icons/airlines/{airline_code}.png.

Does not touch Best Buy, the site registry, or .assets-revision.

Fixes #22.

Verification

python3 -m py_compile sites/google_flights/app.py sites/google_flights/seed_data.py
python3 sites/google_flights/tests/test_airline_logos.py

8/8 tests OK. Flask test_client against the pinned google_flights seed:

• /flights, /search?q=Delta, /flight/<id> return 200 and emit /static/icons/airlines/{IATA}.png
• those pages do not request /static/images/airlines/*.svg
• GET /static/icons/airlines/{AA,DL,…,QF}.png → 200 image/png (PNG signature) for all 23 codes

Live Chromium against standalone Flask on :41007 (pinned seed copied to instance/):

• /flights?from=JFK&to=LAX&depart=2024-01-01 shows the American Airlines gstatic mark
• /search?q=Delta shows the Delta widget on every result row
• /flight/733 “Other flights on this route” shows Qatar, JetBlue, Spirit, Delta, Frontier marks

Docker image rebuild / /reset byte-identity was not re-run here (no Docker daemon; seed DB untouched).

Lineage

Item	Detail
Issue	#22
Stale author PR	#23 (hqhq1025, seed path .svg → .png only)
Stale HF PR	https://huggingface.co/datasets/ChilleD/WebHarbor/discussions/11 (do not merge as a full-site archive)
Fork branch	https://github.com/Lxr-max/WebHarbor/tree/cursor/fix-google-flights-airline-logos-da32