Add a per-widget text-size picker for calendar/tasks legibility

Calendar and tasks pack the most body text at the smallest default
sizes, so those two gear-icon dialogs get a "Text size" card (Normal/
Large/X-Large) alongside the existing Border card -- a new Widget-level
font_scale column with its own POST .../font-scale endpoint, same
Widget-property-not-config-field shape as border_style. Threaded through
every classic (calendar_render.py) and modern (html_render.py/
calendar_html_render.py) size calc via one shared panel_style.
scaled_size() so row heights/max_rows already derived from font size
re-fit around the bigger text automatically.

server/app/calendar_html_render.py

@@ -71,7 +71,8 @@ def _day_section_data(day: date, events: list[dict], tz: ZoneInfo, palette_rgb,
 
 def build_agenda(events: list[dict], browse_offset: int, target_w: int, target_h: int, tz: ZoneInfo,
                  palette_rgb: list | None = None, weather_cities: list[dict] | None = None,
-                 weather_units: str = "fahrenheit", theme_name: str | None = None) -> Image.Image:
+                 weather_units: str = "fahrenheit", theme_name: str | None = None,
+                 font_scale: float = 1.0) -> Image.Image:
     """HTML/CSS-rendered analogue of calendar_render._build_agenda.
 
     Bold-minimal: no card/border/shadow (theme["radius"]/theme["shadow"]
@@ -83,8 +84,8 @@ def build_agenda(events: list[dict], browse_offset: int, target_w: int, target_h
     improvement over the old design, not just a visual one."""
     theme = theme_tokens.resolve_theme(theme_name, "calendar", palette_rgb)
     day = datetime.now(tz).date() + timedelta(days=browse_offset)
-    title_size = max(14, min(target_w, target_h) // 12)
-    body_size = max(11, min(target_w, target_h) // 20)
+    title_size = panel_style.scaled_size(max(14, min(target_w, target_h) // 12), font_scale)
+    body_size = panel_style.scaled_size(max(11, min(target_w, target_h) // 20), font_scale)
     weather_size = max(10, body_size - 2)
     row_h = body_size + 14
     unit_suffix = "F" if weather_units == "fahrenheit" else "C"
@@ -120,7 +121,8 @@ def build_agenda(events: list[dict], browse_offset: int, target_w: int, target_h
 
 def build_today_tomorrow(events: list[dict], browse_offset: int, target_w: int, target_h: int, tz: ZoneInfo,
                          palette_rgb: list | None = None, weather_cities: list[dict] | None = None,
-                         weather_units: str = "fahrenheit", theme_name: str | None = None) -> Image.Image:
+                         weather_units: str = "fahrenheit", theme_name: str | None = None,
+                         font_scale: float = 1.0) -> Image.Image:
     """HTML/CSS-rendered analogue of calendar_render._build_today_tomorrow
     -- two day-sections stacked (see _day_section_data). Bold-minimal, no
     card (see build_agenda's docstring) -- each section's own slim accent
@@ -128,8 +130,8 @@ def build_today_tomorrow(events: list[dict], browse_offset: int, target_w: int,
     theme = theme_tokens.resolve_theme(theme_name, "calendar", palette_rgb)
     start_day = datetime.now(tz).date() + timedelta(days=browse_offset)
     section_h = target_h // 2
-    title_size = max(13, section_h // 8)
-    body_size = max(10, min(target_w, target_h) // 26)
+    title_size = panel_style.scaled_size(max(13, section_h // 8), font_scale)
+    body_size = panel_style.scaled_size(max(10, min(target_w, target_h) // 26), font_scale)
     weather_size = max(9, body_size - 2)
     row_h = body_size + 12
     unit_suffix = "F" if weather_units == "fahrenheit" else "C"
@@ -170,7 +172,7 @@ def build_today_tomorrow(events: list[dict], browse_offset: int, target_w: int,
 def build_week(events: list[dict], browse_offset: int, target_w: int, target_h: int, tz: ZoneInfo,
               week_start: int, palette_rgb: list | None = None, weather_cities: list[dict] | None = None,
               weather_units: str = "fahrenheit", days: int = 7, layout: str = "horizontal",
-              start_offset: int = 0, theme_name: str | None = None) -> Image.Image:
+              start_offset: int = 0, theme_name: str | None = None, font_scale: float = 1.0) -> Image.Image:
     """HTML/CSS-rendered analogue of calendar_render._build_week -- both
     the vertical (stacked day-sections, reusing build_today_tomorrow's
     template with an arbitrary day count) and horizontal (side-by-side
@@ -189,8 +191,8 @@ def build_week(events: list[dict], browse_offset: int, target_w: int, target_h:
 
     if layout == "vertical":
         section_h = target_h // days
-        title_size = max(11, min(20, section_h // 6))
-        body_size = max(9, min(target_w, target_h) // (18 + days))
+        title_size = panel_style.scaled_size(max(11, min(20, section_h // 6)), font_scale)
+        body_size = panel_style.scaled_size(max(9, min(target_w, target_h) // (18 + days)), font_scale)
         weather_size = max(8, body_size - 2)
         row_h = body_size + 10
         accent_h = round(html_render._clamp(min(target_w, target_h) * 0.018, 3, 5))
@@ -221,7 +223,7 @@ def build_week(events: list[dict], browse_offset: int, target_w: int, target_h:
         ]
         return html_render.ordered_dither_regions(rendered, palette_rgb, accent_regions=accent_regions)
 
-    header_size = max(10, min(16, (target_w // days) // 6))
+    header_size = panel_style.scaled_size(max(10, min(16, (target_w // days) // 6)), font_scale)
     chip_size = max(9, header_size - 3)
     weather_size = max(8, chip_size - 1)
     col_w = max(1, (target_w - panel_style.GUTTER * 2) // days)
@@ -265,7 +267,8 @@ def build_week(events: list[dict], browse_offset: int, target_w: int, target_h:
 
 
 def build_month(events: list[dict], browse_offset: int, target_w: int, target_h: int, tz: ZoneInfo,
-               week_start: int, palette_rgb: list | None = None, theme_name: str | None = None) -> Image.Image:
+               week_start: int, palette_rgb: list | None = None, theme_name: str | None = None,
+               font_scale: float = 1.0) -> Image.Image:
     """HTML/CSS-rendered analogue of calendar_render._build_month --
     density dots per day, not literal event text, same reasoning as the
     classic renderer (real text at typical month-cell size is close to
@@ -289,8 +292,8 @@ def build_month(events: list[dict], browse_offset: int, target_w: int, target_h:
     )
     day_names = [n[:3] for n in (WEEKDAY_NAMES[week_start:] + WEEKDAY_NAMES[:week_start])]
 
-    header_size = max(11, min(16, target_h // 30))
-    day_size = max(10, min(15, target_w // 55))
+    header_size = panel_style.scaled_size(max(11, min(16, target_h // 30)), font_scale)
+    day_size = panel_style.scaled_size(max(10, min(15, target_w // 55)), font_scale)
     dot_size = max(4, day_size // 2)
     accent_h = round(html_render._clamp(min(target_w, target_h) * 0.02, 3, 6))
 
@@ -323,7 +326,7 @@ def build_month(events: list[dict], browse_offset: int, target_w: int, target_h:
 def build(events: list[dict], view: str, browse_offset: int, target_w: int, target_h: int, tz: ZoneInfo,
          week_start: int, palette_rgb: list | None = None, weather_cities: list[dict] | None = None,
          weather_units: str = "fahrenheit", week_days: int = 7, week_layout: str = "horizontal",
-         week_start_offset: int = 0, theme_name: str | None = None) -> Image.Image:
+         week_start_offset: int = 0, theme_name: str | None = None, font_scale: float = 1.0) -> Image.Image:
     """Dispatches to the right build_* -- mirrors calendar_render._build's
     exact "month falls back to agenda when it doesn't fit" resolution, so
     a narrow month-mode widget set to modern style still gets a sensible
@@ -334,11 +337,11 @@ def build(events: list[dict], view: str, browse_offset: int, target_w: int, targ
 
     if effective_view == "agenda":
         return build_agenda(events, browse_offset, target_w, target_h, tz, palette_rgb, weather_cities,
-                            weather_units, theme_name)
+                            weather_units, theme_name, font_scale)
     if effective_view == "today_tomorrow":
         return build_today_tomorrow(events, browse_offset, target_w, target_h, tz, palette_rgb, weather_cities,
-                                    weather_units, theme_name)
+                                    weather_units, theme_name, font_scale)
     if effective_view == "week":
         return build_week(events, browse_offset, target_w, target_h, tz, week_start, palette_rgb, weather_cities,
-                          weather_units, week_days, week_layout, week_start_offset, theme_name)
-    return build_month(events, browse_offset, target_w, target_h, tz, week_start, palette_rgb, theme_name)
+                          weather_units, week_days, week_layout, week_start_offset, theme_name, font_scale)
+    return build_month(events, browse_offset, target_w, target_h, tz, week_start, palette_rgb, theme_name, font_scale)