Add a text widget (rich text: bold/italic/underline, per-run color/highlight)

A new self-contained widget type showing user-authored rich text -- no
live upstream to poll, like the static image widget, just word-wrapped
styled text instead of an uploaded image.

The dialog's contenteditable HTML is never stored or replayed as HTML:
app/text_content.py parses it server-side (on save) into a plain
paragraphs-of-styled-runs structure -- the actual sanitization
boundary, since raw HTML never round-trips back into any browser DOM
(the dialog rebuilds its editor from that same JSON via
createElement/textContent). app/widgets/text.py renders it with a
custom word-wrap/shrink-to-fit layout, using real vendored font weights
(app/fonts/NotoSans-{Regular,Bold,Italic,BoldItalic}.ttf, OFL-licensed
like the emoji fonts already there) rather than every other widget's
single ImageFont.load_default() -- the one widget type where that
distinction matters.

server/tests/test_widgets_text.py

@@ -0,0 +1,106 @@
+"""app.widgets.text -- unit-level, no HTTP: constructs Widget/
+TextWidgetConfig rows directly with already-parsed run structures (the
+HTML-parsing step is covered separately in test_text_content.py; the
+HTTP-level config-save/preview endpoints in
+test_widget_config_and_queue_endpoints.py). These tests only exercise
+render()'s own word-wrap/shrink-to-fit/style layout."""
+
+from __future__ import annotations
+
+import time
+
+from app import widgets
+from app.models import Frame, TextWidgetConfig, Widget
+
+
+def _run(text, **overrides) -> dict:
+    run = {"text": text, "bold": False, "italic": False, "underline": False, "color": None, "bg": None}
+    run.update(overrides)
+    return run
+
+
+def _make_widget(db_session, **cfg_kwargs) -> tuple[Frame, Widget]:
+    frame = db_session.get(Frame, 1)
+    widget = Widget(frame_id=frame.id, widget_type="text", x=0, y=0, w=2, h=1,
+                    sort_order=0, created_at=time.time())
+    db_session.add(widget)
+    db_session.flush()
+    db_session.add(TextWidgetConfig(widget_id=widget.id, **cfg_kwargs))
+    db_session.commit()
+    return frame, widget
+
+
+def test_render_shows_a_placeholder_when_never_configured(db_session):
+    frame, widget = _make_widget(db_session)
+    img = widgets.text.render(db_session, frame, widget, 300, 200)
+    assert img.size == (300, 200)
+    assert img.mode == "RGB"
+
+
+def test_render_shows_a_placeholder_for_whitespace_only_content(db_session):
+    frame, widget = _make_widget(db_session, content=[[_run("   ")]])
+    img = widgets.text.render(db_session, frame, widget, 300, 200)
+    assert img.size == (300, 200)
+
+
+def test_render_draws_configured_text(db_session):
+    frame, widget = _make_widget(db_session, content=[[_run("Hello world")]])
+    img = widgets.text.render(db_session, frame, widget, 300, 200)
+    assert img.size == (300, 200)
+    assert img.mode == "RGB"
+    # Not just a blank/placeholder canvas -- some non-background pixel exists.
+    assert img.getcolors(maxcolors=1) is None or img.getcolors()[0][0] != 300 * 200
+
+
+def test_render_respects_background_color(db_session):
+    frame, widget = _make_widget(db_session, content=[[_run("hi")]], background_color="#ff0000")
+    img = widgets.text.render(db_session, frame, widget, 50, 40)
+    assert img.getpixel((0, 0)) == (255, 0, 0)
+
+
+def test_render_shrinks_font_to_fit_a_tiny_box(db_session):
+    long_text = " ".join(["word"] * 40)
+    frame, widget = _make_widget(db_session, content=[[_run(long_text)]], font_size=96)
+    # grid.MIN_FOOTPRINT["text"] is (2, 1) cells -- on an 8x5 grid against
+    # a full 800x480 panel that's a 200x96 box, the smallest a text
+    # widget can actually be placed at.
+    img = widgets.text.render(db_session, frame, widget, 200, 96)
+    assert img.size == (200, 96)
+
+
+def test_render_wraps_across_multiple_paragraphs(db_session):
+    content = [[_run("First paragraph with several words to wrap.")],
+              [_run("Second paragraph, also with text.")]]
+    frame, widget = _make_widget(db_session, content=content)
+    img = widgets.text.render(db_session, frame, widget, 250, 150)
+    assert img.size == (250, 150)
+
+
+def test_render_applies_bold_italic_underline_color_and_highlight(db_session):
+    content = [[
+        _run("bold", bold=True),
+        _run(" "),
+        _run("italic", italic=True),
+        _run(" "),
+        _run("underline", underline=True),
+        _run(" "),
+        _run("colored", color="#cf000f"),
+        _run(" "),
+        _run("highlighted", bg="#ffdb00"),
+    ]]
+    frame, widget = _make_widget(db_session, content=content)
+    img = widgets.text.render(db_session, frame, widget, 400, 150)
+    assert img.size == (400, 150)
+
+
+def test_render_respects_alignment(db_session):
+    for align in ("left", "center", "right"):
+        frame, widget = _make_widget(db_session, content=[[_run("hi")]], align=align)
+        img = widgets.text.render(db_session, frame, widget, 200, 100)
+        assert img.size == (200, 100)
+
+
+def test_no_button_actions():
+    """Fixed authored text -- nothing to advance/back/check."""
+    assert widgets.text.ACTIONS == {}
+    assert widgets.text.ACTION_LABELS == {}