Homepage: give the user page its own login (dankuser)

The homepage user page + shared data now use a dedicated CADDY_HOMEPAGE_HASH
(username dankuser), separate from the shared family password (CADDY_BASICAUTH_HASH,
username dank, still used by the other vhosts) and the operator password
(CADDY_ADMIN_HASH, username frank, the /admin/ page). This lets the homepage be
re-logged independently without touching the other sites. deploy.sh renders the
new placeholder; the .env.example documents all three hashes.

tests/homepage_caddy.bats

@@ -10,8 +10,8 @@ setup() {
     CADDY="$REPO_ROOT/dankclaw/Caddyfile"
 }
 
-@test "the homepage has a root hash and a distinct admin hash (Q18/Q38)" {
-    grep -q "REPLACE_WITH_HASH" "$CADDY"
+@test "the homepage has its own hash and a distinct admin hash" {
+    grep -q "REPLACE_WITH_HOMEPAGE_HASH" "$CADDY"
     grep -q "REPLACE_WITH_ADMIN_HASH" "$CADDY"
 }
 
@@ -43,5 +43,5 @@ setup() {
     # page's credential for these, so the block must accept both users.
     grep -qE "@data[[:space:]]+path[[:space:]]+/services\.json[[:space:]]+/status\.json" "$CADDY"
     grep -qE "handle[[:space:]]+@data" "$CADDY"
-    grep -qE "dank[[:space:]]+REPLACE_WITH_HASH" "$CADDY"
+    grep -qE "dankuser[[:space:]]+REPLACE_WITH_HOMEPAGE_HASH" "$CADDY"
 }