Add adjustable text size and emoji size preferences (#71)

Text was too small on high-DPI screens with no in-app fix beyond
browser zoom. Adds a text-size setting (scales the whole app via a
root font-size percentage), auto-large rendering for emoji-only
messages, and an independent emoji-size preference that also scales
reaction pills without affecting the emoji picker's fixed-size grid.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/app/models/user.py

@@ -19,6 +19,17 @@ class User(Base):
     is_active: Mapped[bool] = mapped_column(Boolean, default=True, nullable=False)
     display_name: Mapped[str | None] = mapped_column(String(50))
     theme: Mapped[str | None] = mapped_column(String(20))
+    # #71: null means "normal" (the pre-existing default before this
+    # setting existed) -- a preset name, not a raw scale factor, so it's
+    # validated/enumerable the same way `theme` already is rather than
+    # accepting an arbitrary float.
+    text_scale: Mapped[str | None] = mapped_column(String(20))
+    # #71: independent of text_scale above -- scales emoji rendered in
+    # message text specifically, not the whole UI (see
+    # frontend/src/components/MessageContent.tsx's --emoji-scale, scoped
+    # to message content only so it can't also inflate the emoji picker's
+    # grid or reaction pills).
+    emoji_scale: Mapped[str | None] = mapped_column(String(20))
     # Only meaningful when theme == "custom" -- which of this user's saved
     # CustomTheme rows (app/models/custom_theme.py) is currently active.
     # Cleared explicitly (not via a DB-level ON DELETE) whenever that theme

backend/app/routers/auth.py

@@ -100,6 +100,10 @@ async def update_profile(
         current_user.display_name = display_name or None
     if "theme" in updates:
         current_user.theme = updates["theme"]
+    if "text_scale" in updates:
+        current_user.text_scale = updates["text_scale"]
+    if "emoji_scale" in updates:
+        current_user.emoji_scale = updates["emoji_scale"]
     if "appear_offline" in updates:
         current_user.appear_offline = updates["appear_offline"]
     await db.commit()

backend/app/schemas/user.py

@@ -23,6 +23,8 @@ class UserRead(BaseModel):
     is_site_admin: bool
     display_name: str | None
     theme: str | None
+    text_scale: str | None
+    emoji_scale: str | None
     # Resolved, not just an id -- the frontend needs the actual palette to
     # paint on load without a second round trip (see lib/theme.ts).
     active_custom_theme: CustomThemeRead | None
@@ -57,6 +59,10 @@ class ProfileUpdate(BaseModel):
     # ownership check; that's POST /api/custom-themes/{id}/activate, not a
     # bare theme name with nothing to point it at.
     theme: Literal["dark", "light", "midnight", "sunset"] | None = Field(default=None)
+    # #71: kept in sync with frontend/src/lib/theme.ts's TEXT_SCALE_PERCENT map.
+    text_scale: Literal["small", "normal", "large", "xlarge"] | None = Field(default=None)
+    # #71: kept in sync with MessageContent.tsx's EMOJI_SCALE_MULTIPLIER map.
+    emoji_scale: Literal["small", "normal", "large", "xlarge"] | None = Field(default=None)
     appear_offline: bool | None = Field(default=None)