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/widgets/photos.py

@@ -8,7 +8,23 @@ take down the whole panel's render just because one region out of
 several couldn't be composed this cycle; it falls back to a small
 placeholder instead, the same resilience calendar mode's old photo-inlay
 already had (see routers/device.py's `except HTTPException: pass` around
-its own inlay fetch)."""
+its own inlay fetch).
+
+Unlike every other widget type, render() quantizes its own output
+(against Frame.photo_palette_rgb/photo_dither_strength, not the main
+palette_rgb/dither_strength the rest of the frame uses) before
+returning, so a frame can tune its other widgets' look (e.g. the
+"modern" HTML-rendered widgets' Bayer dithering) independently of
+whatever looks best for actual photographs -- see image_pipeline.
+render_panel's docstring for why this is safe to do per-widget without
+a shared-canvas seam risk. One small, accepted edge case: widget
+borders are always drawn afterward (routers/device.py's
+_render_one_widget) against the *main* palette_rgb, so a border on a
+photos widget whose photo_palette_rgb genuinely diverges from
+palette_rgb can sit against already-quantized-to-a-different-reference
+photo pixels -- cosmetically arguable, not a bug, and not worth
+special-casing border resolution for what's a deliberate, uncommon
+customization."""
 
 from __future__ import annotations
 
@@ -18,7 +34,7 @@ from sqlalchemy.orm import Session
 
 from .. import photo_queue, quiet_hours
 from ..db import widget_locked
-from ..image_pipeline import compose_into
+from ..image_pipeline import _quantize, compose_into
 from ..models import Frame, PhotoWidgetConfig, Widget
 from ..routers.common import fetch_source_and_faces, immich_client_for, list_assets
 from ._shared import placeholder_image
@@ -50,7 +66,8 @@ def render(db: Session, frame: Frame, widget: Widget, target_w: int, target_h: i
     except HTTPException as e:
         return placeholder_image(target_w, target_h, ["Photos widget", str(e.detail)[:40]])
 
-    return compose_into(source, faces, target_w, target_h, cfg.display_mode)
+    composed = compose_into(source, faces, target_w, target_h, cfg.display_mode)
+    return _quantize(composed, frame.photo_palette_rgb, frame.photo_dither_strength).convert("RGB")
 
 
 def _advance(db: Session, frame: Frame, widget: Widget) -> None: