Expose encoding quality and overlay durations in sky-cam.conf

Adds six CRF vars, AUDIO_BITRATE, and three MONTAGE_* overlay durations.
Values match previous hardcoded defaults so behavior is unchanged.

The same CRF appeared in several scripts but with intentionally different
values per purpose (28 for draft intermediates, 26 for polished output).
Each script's CRF is now its own variable in conf, so changing one never
silently changes another.

https://claude.ai/code/session_01C4jbd3waXG3eKZYbGUjLUQ

sky-cam.conf

@@ -209,6 +209,32 @@ SUNRISE_TARGET_SECS=10
 FULLDAY_FPS=5        # frame rate of the timelapse video
 RETENTION_DAYS=10    # delete full-day videos older than this many days
 
+# ── Video encoding quality ────────────────────────────────────────────────────
+# FFmpeg CRF: lower = higher quality / larger files.  Typical range 18–30.
+#   18 ≈ visually lossless     23 = ffmpeg default     28 = smaller/lower
+# Different scripts use different defaults by design — intermediate/draft
+# encodings use a higher CRF (smaller files, quality less critical), while
+# final "polished" outputs use a lower CRF for better quality.
+# Each is independent — changing one does NOT change the others.
+#
+CRF_SUNRISE=28        # daily_sunrise_video.sh   — daily Mattermost upload
+CRF_FULLDAY=28        # fullday-video.sh         — full-day timelapse
+CRF_SEASONS_RAW=28    # 4-seasons.sh             — raw concat before speed-adjust
+CRF_SEASONS_FINAL=26  # 4-seasons.sh             — final daily clip (goes into montage)
+CRF_MONTAGE=26        # montage-mvt.sh           — concat and speed-adjust and final
+AUDIO_BITRATE=192k    # montage-mvt.sh           — music track on movement montages
+
+# ── Montage attribution overlay ───────────────────────────────────────────────
+# A translucent bar across the top of each movement montage, naming the
+# music source ("The Four Seasons — Antonio Vivaldi ...").
+# Appears for MONTAGE_ATTR_DUR seconds from the start, with ATTR_FADE-second
+# fade in and fade out.  FADE_DUR controls the video/audio fade in/out at
+# the very start and very end of the montage.
+#
+MONTAGE_FADE_DUR=2.0   # video + audio fade in/out (seconds)
+MONTAGE_ATTR_DUR=6     # attribution overlay total duration (seconds)
+MONTAGE_ATTR_FADE=1    # attribution fade-in and fade-out length (seconds)
+
 # ── Mattermost — daily sunrise upload ─────────────────────────────────────────
 mattermost_url=https://your-mattermost-server.example.com
 access_token=your-access-token-here