Add core engine: tarot + astrology reading generator with CLI and i18n

Plain-C, dependency-free engine that produces a personalized daily
Celtic Cross tarot spread and natal-chart/transit astrology reading,
plus a standalone CLI (dist/deck-engine) and run.sh wrapper. Includes
English/German output via a simple key=value translation format, and
docs/diagrams describing the architecture and I/O.

engine/scripts/user.properties.template

@@ -0,0 +1,24 @@
+# deck-in-a-dash user properties
+#
+# Fill in your birth details below, then run ./run.sh (or ./run.sh html).
+# This file is only copied here once by the build - it will not be
+# overwritten by later builds, so it's safe to edit in place.
+#
+# birth_date        Birth date, local calendar, YYYY-MM-DD
+# birth_time        Birth time, local clock, 24h HH:MM
+# birth_utc_offset  Hours to ADD to UTC to get your birth's local time
+#                    (e.g. 2 for Central European Summer Time)
+# birth_lat         Birth location latitude, decimal degrees, north positive
+# birth_lon         Birth location longitude, decimal degrees, east positive
+# lang              Reading language code - matches a file named
+#                    <code>.lang in dist/i18n/ (see engine/i18n/ for the
+#                    source files, currently "en" and "de"). Optional,
+#                    defaults to "en"; unknown codes silently fall back
+#                    to English too.
+
+birth_date=YOUR_BIRTH_DATE_HERE
+birth_time=YOUR_BIRTH_TIME_HERE
+birth_utc_offset=YOUR_UTC_OFFSET_HERE
+birth_lat=YOUR_LATITUDE_HERE
+birth_lon=YOUR_LONGITUDE_HERE
+lang=en