Fix first-run blockers: MOVIES_DIR path, CAM_NAME, .env for Python, eval safety

daily_sunrise_video.sh: use \$MOVIES_DIR instead of \$BASE_DIR/movies so the
override in sky-cam.conf is respected when videos live on a separate drive.

capture.sh: default camera name falls back to \$SUNRISE_CAM (not the
undefined \$CAM_NAME) when no argument is passed.

sunrise2mm.py: also loads .env after sky-cam.conf so Mattermost credentials
moved to .env are actually visible to the upload script.

sunrise.py: raise a clear error message when LATITUDE/LONGITUDE/TIMEZONE
are missing from sky-cam.conf instead of an opaque KeyError.

4-seasons.sh, montage-mvt.sh: capture season_info.py output before eval so
a Python failure exits cleanly with a diagnostic message rather than
silently continuing with undefined variables.

bootstrap.sh: add system package install step (ffmpeg bc fonts-dejavu) and
show the .env setup step after install.sh generates .env.example.

README.md: correct Python package names and add fonts-dejavu dependency.

https://claude.ai/code/session_01C4jbd3waXG3eKZYbGUjLUQ

montage-mvt.sh

@@ -39,7 +39,11 @@ ATTR_FADE="$MONTAGE_ATTR_FADE"
 
 # ── Season / movement info ────────────────────────────────────────────────────
 DATE_ARG="${1:-}"
-eval "$(python3 "$SCRIPT_DIR/season_info.py" ${DATE_ARG:+"$DATE_ARG"})"
+_season_info="$(python3 "$SCRIPT_DIR/season_info.py" ${DATE_ARG:+"$DATE_ARG"})" || {
+    echo "Error: season_info.py failed — check Python dependencies (suntime pytz)"
+    exit 1
+}
+eval "$_season_info"
 # Provides: SEASON  MVT_NUM  DAY_OF_MVT  DAYS_IN_MVT  MVT_START  MVT_END
 #           IS_LAST_DAY  ASTRO_YEAR
 echo "Season=$SEASON  Mvt=$MVT_NUM  Year=$ASTRO_YEAR  (ref: ${DATE_ARG:-today})"