Compact home page entries; set up Compose for Arcane git sync

Podium, Spotlight and Grid render smaller on the home page on desktop so
one entry no longer fills the screen; list pages keep full size.

Compose now builds on every deploy (pull_policy: build), stores data in
the canon-data named volume outside the synced folder (CANON_DATA_PATH
overrides), and takes optional bind/port/version settings.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.env.example

@@ -20,3 +20,13 @@ CANON_IGDB_CLIENT_SECRET=
 # CANON_HOST=0.0.0.0   # all network interfaces; 127.0.0.1 = this machine only
 # CANON_PORT=4242
 # CANON_LOG_LEVEL=debug
+
+# ---- Docker Compose only (not read by Canon itself) ----
+# Where the database and images live. Default: the canon_canon-data volume.
+# Use an absolute host path to keep them in a folder (writable by UID 1000).
+# CANON_DATA_PATH=/srv/canon
+# Host address and port to publish on.
+# CANON_BIND=0.0.0.0
+# CANON_PUBLISH_PORT=4242
+# Version label baked into the image at build time.
+# CANON_VERSION=dev