Add per-event NASA moon images with east-sky cloud veil

Three changes driven by the same goal: make each monthly moon post
look like east captured it at that exact moment.

Tighter illumination windows (±4% of target phase):
  Full moon:   95% → 96–100%  (was a 5-point band; now hugs exact full)
  Quarters:    40–65% → 46–54%  (was a 25-point band; now ±4% of 50%)
This ensures the NASA Dial-a-Moon render timestamp is pulled within
4 percentage points of the true phase, making the fetched image
genuinely represent that night's moon.  One fresh fetch per event,
~3/month, cached by hour — never reused across months.

Atmospheric cloud veil from east's surrounding sky:
  _extract_cloud_veil() samples the annular sky region just outside
  east's moon disk (2×–5× radius), scales it to the output frame,
  blurs heavily (GaussianBlur r≈output_width/10) so it reads as haze
  rather than an upscaled photo, then blends it over the NASA composite
  at an opacity proportional to sky brightness:
    sky < 5% mean brightness → no veil (clear dark night)
    sky ~10%                 → ~17% veil (thin haze / airglow)
    sky ≥ 20%                → 40% veil (max, MOON_CLOUD_OVERLAY_MAX_OPACITY)
  After the veil pass the NASA moon disk is re-pasted sharply so the
  haze sits naturally behind the crisp lunar surface.
  This is the honest answer to "east can't capture high-res clouds":
  east's real atmospheric fingerprint becomes the veil texture.

New sky-cam.conf keys:
  MOON_CLOUD_OVERLAY_ENABLED=true
  MOON_CLOUD_OVERLAY_MAX_OPACITY=0.40
  #MOON_CLOUD_OVERLAY_BLUR=0  (0 = auto)

https://claude.ai/code/session_01HkTxpNSTWtViZzxbrbKytR

sky-cam.conf

@@ -499,15 +499,15 @@ MOON_FULL_POST_DELAY_DAYS=3
 # Quarter (half-moon) tuning ──────────────────────────────────────────────────
 # 2 = waits for D-1, D, D+1 nights, runs the morning of D+2.
 MOON_QUARTER_POST_DELAY_DAYS=2
-MOON_QUARTER_MIN_ILLUMINATION=0.40 # ~50% ± 10% covers the day around exact quarter
-MOON_QUARTER_MAX_ILLUMINATION=0.65
+MOON_QUARTER_MIN_ILLUMINATION=0.46 # ±4% of 50%: waxing/waning within 4% of exact quarter
+MOON_QUARTER_MAX_ILLUMINATION=0.54
 
 # Frame-acceptance thresholds — a candidate must beat all three to qualify.
 # Lower = more permissive (accept hazier nights / lower moon).  If you find
 # the script never finds a clear shot, loosen these.
 MOON_MIN_QUALITY=0.55              # 0..1 from moon_detect (roundness × halo × isolation)
 MOON_MIN_ALTITUDE_DEG=15           # below this the moon is in trees / on the horizon
-MOON_FULL_MIN_ILLUMINATION=0.95    # 0..1 — ~95% lit covers ±2 days from exact full
+MOON_FULL_MIN_ILLUMINATION=0.96    # ±4% of 100%: accept 96–100% illumination for full moon
 
 # Output frame.  Default 1920×1080 to match the sunrise videos.
 MOON_OUTPUT_W=1920
@@ -524,6 +524,27 @@ MOON_HEIGHT_PCT=0.92               # moon disk fills this fraction of frame heig
 MOON_DIALAMOON_TARGET_PX=2048      # cached PNG longest side; downsampled on save
 MOON_DIALAMOON_TIMEOUT_SEC=30
 
+# Atmospheric cloud veil ──────────────────────────────────────────────────────
+# When east verifies a moon sighting, the surrounding sky region (annulus
+# just outside the moon disk) is sampled and scaled to fill the output frame,
+# then blurred heavily so it reads as atmospheric haze rather than an upscaled
+# photo.  The result is blended over the NASA composite at an opacity
+# proportional to how bright that sky patch was — dark clear sky adds nothing,
+# thin clouds add a gentle veil, bright overcast reaches MOON_CLOUD_OVERLAY_MAX_OPACITY.
+#
+# This is the honest solution to "east doesn't capture high-res clouds": we use
+# east's actual sky as an atmospheric fingerprint rather than pretending to
+# photograph cloud detail that isn't there.
+#
+# Opacity scale:
+#   mean sky brightness < 5%   → no veil (clear dark sky)
+#   mean sky brightness   10%  → ~17% veil  (thin haze / airglow)
+#   mean sky brightness ≥ 20%  → MOON_CLOUD_OVERLAY_MAX_OPACITY (40%)
+#
+MOON_CLOUD_OVERLAY_ENABLED=true
+MOON_CLOUD_OVERLAY_MAX_OPACITY=0.40  # 0.0–1.0; never fully obscures the NASA render
+#MOON_CLOUD_OVERLAY_BLUR=0           # blur radius in px; 0 = auto (output_width / 10)
+
 # ── Mattermost — daily sunrise upload ─────────────────────────────────────────
 # mattermost_url, access_token, channel_id go in .env (see bottom of this file).