web: reader link to the left, downloads into a "pobierz" disclosure

Finish the top-bar rework. The reader entry point now leads the controls
bar on the far left (it was in the right-hand cluster); settings stays in
the top-right cluster.

The flat "download: txt md pdf · kalendarz" strip becomes a single
"pobierz" summary that opens a small floating panel with two rows:
 - a month calendar with its own month + year <select> pickers (localised
   month names, both pre-selected from the shown date) and a PDF button
   that hits /calendar?month=YYYY-MM;
 - the shown day's readings as txt/md/pdf, labelled with the date.

The panel is absolutely positioned under the link so opening it doesn't
reflow the bar. indexData gains MonthOpts/YearOpts (a calOpt list); the
year picker is a small window around the shown year.

1 files changed, 28 insertions, 3 deletions

diff --git a/internal/web/static/base.css b/internal/web/static/base.css
index 757e935..b5f4f13 100644
--- a/internal/web/static/base.css
+++ b/internal/web/static/base.css
@@ -322,9 +322,34 @@ a {
   gap: var(--space-2);
 }
 
-/* Export links (download the readings). */
-.export { font-family: var(--font-ui); font-size: 0.85rem; }
-.export a { margin: 0 0.15rem; }
+/* "pobierz" disclosure: a summary styled as a nav link that reveals a small
+ * floating panel of download options (a month calendar with its own month/year
+ * pickers, and the shown day's txt/md/pdf export). The panel is absolutely
+ * positioned under the link so opening it never reflows the controls bar.
+ * Colour (border/background) is the theme's, via the shared --bg/--fg tokens. */
+.export { position: relative; font-family: var(--font-ui); font-size: 0.85rem; }
+.export > summary { cursor: pointer; list-style: none; }
+.export > summary::-webkit-details-marker { display: none; }
+.export > summary::after { content: " \25be"; } /* down caret */
+.export[open] > summary::after { content: " \25b4"; } /* up caret */
+.export-panel {
+  position: absolute;
+  right: 0;
+  top: calc(100% + 0.35rem);
+  z-index: 10;
+  display: flex;
+  flex-direction: column;
+  gap: var(--space-1);
+  padding: var(--space-2);
+  border-width: 1px;
+  border-style: solid;
+  background: var(--bg);
+  white-space: nowrap;
+}
+.export-row { display: flex; align-items: center; gap: 0.5rem; }
+.export-row .export-label { font-weight: 600; }
+.export-panel select { font: inherit; }
+.export-panel a { margin: 0; }
 
 /* Bookmark marker: a red "*" flagging a bookmarked verse in the reader. A fixed
  * semantic red (not a theme colour), visible on light and dark themes alike. */