Roll out "modern" HTML/CSS render style to every widget except photos

Extends weather's experimental Chromium+Jinja2 render style to battery,
text, tasks, static image, whiteboard, and calendar (all four view
modes -- agenda/today_tomorrow/week/month), and gives the photos widget
its own genuinely independent palette + dithering strength.

Photos: Frame.photo_palette_rgb/photo_dither_strength (mirroring the
existing palette_rgb/dither_strength), with a second "Photos
configuration" card in Advanced Configuration. widgets/photos.py's
render() quantizes itself against these before returning -- no
render_panel changes needed, since photos is the only widget that
genuinely needs a different reference palette and can carry that
itself, the same way modern-style widgets already self-dither via
ordered_dither.

Battery/text/tasks/static image/whiteboard: same render_style pattern
weather established (render_style column, html_render.py build
function, Jinja2 template, dialog toggle). Static image/whiteboard get
their first-ever visual chrome (a rounded-corner shadowed card,
shared framed_image.html.jinja) since classic draws them with zero
frame at all. Fixed the same "preview endpoint bypasses render_style"
bug weather originally shipped with, for tasks/static/whiteboard/
calendar's preview endpoints.

Calendar: own module (app/calendar_html_render.py, mirroring
calendar_render.py's separation from the simpler widgets) covering all
four view modes, not just agenda -- reuses calendar_render's own
private helpers so event colors/times/weather/month-grid math match
classic exactly. Found and fixed two real cross-day layout bugs along
the way: a per-day header height that varied based on whether that
specific day had a weather entry (misaligning where every other day's
event rows started across the week/month grid), and regular-weight
small text being fragile under Bayer ordered dithering (out-of-month
day numbers degraded into unrecognizable speckle) -- fixed by using
bold everywhere and de-emphasizing via size instead of weight/gray,
since gray text has the same dithering fragility this project's PIL
renderers already avoid for exactly this reason.

Migrations 32-38 (Frame's two new columns, then one render_style column
per widget config table). 452 tests passing, including new dispatch/
migration coverage per widget type and a dedicated photos test proving
photo_palette_rgb produces genuinely independent quantization from the
frame's main palette_rgb.

server/app/migration.py

@@ -814,6 +814,72 @@ def _migration_31(conn) -> None:
         conn.execute(text("ALTER TABLE weather_widget_configs ADD COLUMN render_style TEXT NOT NULL DEFAULT 'classic'"))
 
 
+def _migration_32(conn) -> None:
+    """Photos widget's own independent palette/dithering (models.Frame.
+    photo_palette_rgb/photo_dither_strength -- see widgets/photos.py's
+    render()). NULL/1.0 defaults reproduce the exact previous rendering
+    (same reference palette/strength as the main fields) until a frame's
+    Configuration tab sets them differently.
+
+    Guarded per-column, same reasoning as migration 30/31's own comments."""
+    existing = {c["name"] for c in inspect(conn).get_columns("frames")}
+    if "photo_palette_rgb" not in existing:
+        conn.execute(text("ALTER TABLE frames ADD COLUMN photo_palette_rgb TEXT"))
+    if "photo_dither_strength" not in existing:
+        conn.execute(text("ALTER TABLE frames ADD COLUMN photo_dither_strength REAL NOT NULL DEFAULT 1.0"))
+
+
+def _migration_33(conn) -> None:
+    """Battery widget render style (models.BatteryWidgetConfig.
+    render_style) -- same shape as migration 31's weather one. Every
+    existing battery widget defaults to "classic", no behavior change."""
+    existing = {c["name"] for c in inspect(conn).get_columns("battery_widget_configs")}
+    if "render_style" not in existing:
+        conn.execute(text("ALTER TABLE battery_widget_configs ADD COLUMN render_style TEXT NOT NULL DEFAULT 'classic'"))
+
+
+def _migration_34(conn) -> None:
+    """Text widget render style (models.TextWidgetConfig.render_style) --
+    same shape as migration 31/33. Every existing text widget defaults to
+    "classic", no behavior change."""
+    existing = {c["name"] for c in inspect(conn).get_columns("text_widget_configs")}
+    if "render_style" not in existing:
+        conn.execute(text("ALTER TABLE text_widget_configs ADD COLUMN render_style TEXT NOT NULL DEFAULT 'classic'"))
+
+
+def _migration_35(conn) -> None:
+    """Tasks widget render style (models.TaskWidgetConfig.render_style)
+    -- same shape as migration 31/33/34. Every existing tasks widget
+    defaults to "classic", no behavior change."""
+    existing = {c["name"] for c in inspect(conn).get_columns("task_widget_configs")}
+    if "render_style" not in existing:
+        conn.execute(text("ALTER TABLE task_widget_configs ADD COLUMN render_style TEXT NOT NULL DEFAULT 'classic'"))
+
+
+def _migration_36(conn) -> None:
+    """Static image widget render style (models.StaticWidgetConfig.
+    render_style) -- same shape as migration 31/33/34/35."""
+    existing = {c["name"] for c in inspect(conn).get_columns("static_widget_configs")}
+    if "render_style" not in existing:
+        conn.execute(text("ALTER TABLE static_widget_configs ADD COLUMN render_style TEXT NOT NULL DEFAULT 'classic'"))
+
+
+def _migration_37(conn) -> None:
+    """Whiteboard widget render style (models.WhiteboardWidgetConfig.
+    render_style) -- same shape as migration 36."""
+    existing = {c["name"] for c in inspect(conn).get_columns("whiteboard_widget_configs")}
+    if "render_style" not in existing:
+        conn.execute(text("ALTER TABLE whiteboard_widget_configs ADD COLUMN render_style TEXT NOT NULL DEFAULT 'classic'"))
+
+
+def _migration_38(conn) -> None:
+    """Calendar widget render style (models.CalendarWidgetConfig.
+    render_style) -- same shape as migration 31/33/34/35/36/37."""
+    existing = {c["name"] for c in inspect(conn).get_columns("calendar_widget_configs")}
+    if "render_style" not in existing:
+        conn.execute(text("ALTER TABLE calendar_widget_configs ADD COLUMN render_style TEXT NOT NULL DEFAULT 'classic'"))
+
+
 MIGRATIONS = [
     (1, _migration_1),
     (2, _migration_2),
@@ -846,6 +912,13 @@ MIGRATIONS = [
     (29, _migration_29),
     (30, _migration_30),
     (31, _migration_31),
+    (32, _migration_32),
+    (33, _migration_33),
+    (34, _migration_34),
+    (35, _migration_35),
+    (36, _migration_36),
+    (37, _migration_37),
+    (38, _migration_38),
 ]