feat(auth,a11y): Telegram CloudStorage token recovery + blocking-screen a11y

Telegram CloudStorage token recovery (resilience against WebView localStorage wipes):
- mirror the refresh token to per-user CloudStorage on login, remove it on logout
- restoreRefreshTokenFromCloud() recovers the refresh token in initialize() when
  localStorage is empty, then the normal refresh flow re-establishes the session
- move the initialize() bootstrap call from auth.ts module-load into main.tsx after
  the Telegram SDK init(), since launch params + CloudStorage are unavailable before init
- best-effort: no-ops outside Telegram and on any error -> falls back to prior behavior

Accessibility:
- role=alertdialog + aria-modal + aria-labelledby + focus management (useFocusTrap)
  on Maintenance, Blacklisted, ChannelSubscription and AccountDeleted blocking screens
- aria-label on ColorPicker Hue/Saturation/Lightness range inputs

src/components/ColorPicker.tsx

@@ -281,6 +281,7 @@ export function ColorPicker({ value, onChange, label, description, disabled }: C
             max="360"
             value={hsl.h}
             onChange={handleHueChange}
+            aria-label="Hue"
             className="h-3 w-full cursor-pointer appearance-none rounded-full"
             style={{
               background:
@@ -301,6 +302,7 @@ export function ColorPicker({ value, onChange, label, description, disabled }: C
             max="100"
             value={hsl.s}
             onChange={handleSaturationChange}
+            aria-label="Saturation"
             className="h-3 w-full cursor-pointer appearance-none rounded-full"
             style={{
               background: `linear-gradient(to right, hsl(${hsl.h}, 0%, ${hsl.l}%), hsl(${hsl.h}, 100%, ${hsl.l}%))`,
@@ -320,6 +322,7 @@ export function ColorPicker({ value, onChange, label, description, disabled }: C
             max="100"
             value={hsl.l}
             onChange={handleLightnessChange}
+            aria-label="Lightness"
             className="h-3 w-full cursor-pointer appearance-none rounded-full"
             style={{
               background: `linear-gradient(to right, #000000, hsl(${hsl.h}, ${hsl.s}%, 50%), #ffffff)`,