feat(theme): tema Compose con paleta Rachita y fuentes descargables

- Color.kt: paleta completa del PRD §6.1 (coral/menta/sol/lila/crema/tinta/noche)
- Type.kt: Baloo 2 + Nunito vía Google Fonts provider, escala del PRD §6.2
- Shape.kt: radios 14-24dp + píldora; Theme.kt: MaterialTheme light único

app/app/src/main/java/mx/paputec/rachita/ui/theme/Color.kt

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+package mx.paputec.rachita.ui.theme
+
+import androidx.compose.ui.graphics.Color
+
+// Primary brand colors (PRD §6.1) — used by CTAs, mascot, streak flame.
+val Coral = Color(0xFFFF8A66)
+val CoralIntense = Color(0xFFFF6B3D)
+val CoralSoft = Color(0xFFFFE0D5)
+
+// Secondary — habits, cat mascot, gallery CTA.
+val Mint = Color(0xFF3FB8AE)
+val MintSoft = Color(0xFFD6F3F0)
+
+// Sun / XP / rabbit mascot.
+val Sun = Color(0xFFFBC24E)
+val SunDeep = Color(0xFFF4B63E)
+
+// Museum, charging notifications.
+val Lilac = Color(0xFF8C7CE8)
+val LilacSoft = Color(0xFFE7E3FB)
+
+// Success + charging bar.
+val SuccessGreen = Color(0xFF46C98B)
+val ChargingGreen = Color(0xFF9BE36D)
+
+// Alerts item.
+val Pink = Color(0xFFFF6B8A)
+
+// Backgrounds.
+val CreamBackground = Color(0xFFFFF6EE)
+val CreamCard = Color(0xFFFFE9DF)
+val CreamCardSoft = Color(0xFFFFF1E8)
+
+// Text.
+val Ink = Color(0xFF43352F)
+val WarmGrey = Color(0xFFA4938A)
+val WarmGreyDeep = Color(0xFF8A7A72)
+
+// Card border for secondary CTAs.
+val CardBorder = Color(0xFFEBDFD7)
+
+// Night palette for charging lock screen (module 3, later step).
+val Night = Color(0xFF2A2350)
+val NightGradientStart = Color(0xFF39306E)
+val NightGradientMid = Color(0xFF5A4E97)
+val NightGradientEnd = Color(0xFFB98FC4)

app/app/src/main/java/mx/paputec/rachita/ui/theme/Shape.kt

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+package mx.paputec.rachita.ui.theme
+
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material3.Shapes
+import androidx.compose.ui.unit.dp
+
+// Radii scale from PRD §6.3: 14–24 dp on cards, 999 dp on pills.
+val RachitaShapes = Shapes(
+    extraSmall = RoundedCornerShape(8.dp),
+    small = RoundedCornerShape(14.dp),
+    medium = RoundedCornerShape(18.dp),
+    large = RoundedCornerShape(24.dp),
+    extraLarge = RoundedCornerShape(32.dp),
+)
+
+val PillShape = RoundedCornerShape(999.dp)

app/app/src/main/java/mx/paputec/rachita/ui/theme/Theme.kt

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+package mx.paputec.rachita.ui.theme
+
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.lightColorScheme
+import androidx.compose.runtime.Composable
+
+// Rachita is landscape, single light theme in v1 — no dark mode yet (out of scope
+// per sprint 1). Colors resolved via the palette in Color.kt.
+private val LightColors = lightColorScheme(
+    primary = Coral,
+    onPrimary = CreamBackground,
+    primaryContainer = CoralSoft,
+    onPrimaryContainer = Ink,
+
+    secondary = Mint,
+    onSecondary = CreamBackground,
+    secondaryContainer = MintSoft,
+    onSecondaryContainer = Ink,
+
+    tertiary = Lilac,
+    onTertiary = CreamBackground,
+    tertiaryContainer = LilacSoft,
+    onTertiaryContainer = Ink,
+
+    background = CreamBackground,
+    onBackground = Ink,
+
+    surface = CreamBackground,
+    onSurface = Ink,
+    surfaceVariant = CreamCardSoft,
+    onSurfaceVariant = WarmGreyDeep,
+
+    outline = CardBorder,
+    outlineVariant = CardBorder,
+
+    error = CoralIntense,
+    onError = CreamBackground,
+)
+
+@Composable
+fun RachitaTheme(content: @Composable () -> Unit) {
+    MaterialTheme(
+        colorScheme = LightColors,
+        typography = RachitaTypography,
+        shapes = RachitaShapes,
+        content = content,
+    )
+}

app/app/src/main/java/mx/paputec/rachita/ui/theme/Type.kt

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+package mx.paputec.rachita.ui.theme
+
+import androidx.compose.material3.Typography
+import androidx.compose.ui.text.TextStyle
+import androidx.compose.ui.text.font.FontFamily
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.googlefonts.Font
+import androidx.compose.ui.text.googlefonts.GoogleFont
+import androidx.compose.ui.unit.sp
+import mx.paputec.rachita.R
+
+// Downloadable Fonts via Google Fonts provider (androidx.compose.ui:ui-text-google-fonts).
+// The provider certs live in res/values/font_certs.xml. Baloo 2 for display / headings,
+// Nunito for body copy — matches PRD §6.2.
+private val GoogleFontsProvider = GoogleFont.Provider(
+    providerAuthority = "com.google.android.gms.fonts",
+    providerPackage = "com.google.android.gms",
+    certificates = R.array.com_google_android_gms_fonts_certs,
+)
+
+private val Baloo2 = FontFamily(
+    Font(googleFont = GoogleFont("Baloo 2"), fontProvider = GoogleFontsProvider, weight = FontWeight.Medium),
+    Font(googleFont = GoogleFont("Baloo 2"), fontProvider = GoogleFontsProvider, weight = FontWeight.SemiBold),
+    Font(googleFont = GoogleFont("Baloo 2"), fontProvider = GoogleFontsProvider, weight = FontWeight.Bold),
+    Font(googleFont = GoogleFont("Baloo 2"), fontProvider = GoogleFontsProvider, weight = FontWeight.ExtraBold),
+)
+
+private val Nunito = FontFamily(
+    Font(googleFont = GoogleFont("Nunito"), fontProvider = GoogleFontsProvider, weight = FontWeight.Normal),
+    Font(googleFont = GoogleFont("Nunito"), fontProvider = GoogleFontsProvider, weight = FontWeight.Medium),
+    Font(googleFont = GoogleFont("Nunito"), fontProvider = GoogleFontsProvider, weight = FontWeight.SemiBold),
+    Font(googleFont = GoogleFont("Nunito"), fontProvider = GoogleFontsProvider, weight = FontWeight.Bold),
+    Font(googleFont = GoogleFont("Nunito"), fontProvider = GoogleFontsProvider, weight = FontWeight.ExtraBold),
+)
+
+// Type scale from PRD §6.2: display/title 26–34 sp, streak numbers 42–92 sp,
+// habit names ~23 sp, body 13–16 sp, captions 11–12 sp.
+val RachitaTypography = Typography(
+    displayLarge = TextStyle(fontFamily = Baloo2, fontWeight = FontWeight.ExtraBold, fontSize = 92.sp, color = Ink),
+    displayMedium = TextStyle(fontFamily = Baloo2, fontWeight = FontWeight.ExtraBold, fontSize = 64.sp, color = Ink),
+    displaySmall = TextStyle(fontFamily = Baloo2, fontWeight = FontWeight.Bold, fontSize = 42.sp, color = Ink),
+
+    headlineLarge = TextStyle(fontFamily = Baloo2, fontWeight = FontWeight.Bold, fontSize = 34.sp, color = Ink),
+    headlineMedium = TextStyle(fontFamily = Baloo2, fontWeight = FontWeight.Bold, fontSize = 30.sp, color = Ink),
+    headlineSmall = TextStyle(fontFamily = Baloo2, fontWeight = FontWeight.Bold, fontSize = 26.sp, color = Ink),
+
+    titleLarge = TextStyle(fontFamily = Baloo2, fontWeight = FontWeight.SemiBold, fontSize = 23.sp, color = Ink),
+    titleMedium = TextStyle(fontFamily = Baloo2, fontWeight = FontWeight.SemiBold, fontSize = 20.sp, color = Ink),
+    titleSmall = TextStyle(fontFamily = Baloo2, fontWeight = FontWeight.SemiBold, fontSize = 16.sp, color = Ink),
+
+    bodyLarge = TextStyle(fontFamily = Nunito, fontWeight = FontWeight.SemiBold, fontSize = 16.sp, color = Ink),
+    bodyMedium = TextStyle(fontFamily = Nunito, fontWeight = FontWeight.Medium, fontSize = 14.sp, color = Ink),
+    bodySmall = TextStyle(fontFamily = Nunito, fontWeight = FontWeight.Medium, fontSize = 13.sp, color = WarmGreyDeep),
+
+    labelLarge = TextStyle(fontFamily = Baloo2, fontWeight = FontWeight.Bold, fontSize = 16.sp, color = Ink),
+    labelMedium = TextStyle(fontFamily = Nunito, fontWeight = FontWeight.Bold, fontSize = 12.sp, color = Ink),
+    labelSmall = TextStyle(fontFamily = Nunito, fontWeight = FontWeight.SemiBold, fontSize = 11.sp, color = WarmGreyDeep),
+)