feat(design): surface phase — Lucide icons, input radius, Illuminated Transcript, ActionColors

Per-screen application of the design system to the Flutter app.
Mirrors the web's surface phase landed in FabledScribe v26.04.28.1.
Foundation port shipped in 0f05f47; this is the surface work.

Lucide icon migration
- Added lucide_icons ^0.257.0 dependency
- 107 Material Icons references → LucideIcons across 21 files. Drop-in
  IconData swap (Icon(LucideIcons.X) instead of Icon(Icons.x)).
- Lucide import added to each touched file.

Input border radius
- theme.dart inputDecorationTheme borderRadius 24 → 8 in both light
  and dark themes. Doc says radius-md (8px) for inputs; previous pill
  shape was Material default that the doc deviates from.

Illuminated Transcript pattern (ChatMessageBubble)
- User bubble: accent-tinted border → neutral Pewter (scheme.outline).
  Asymmetric corner already correct (bottomRight 4px).
- Assistant bubble: topLeft corner 4 → 16; only bottomLeft stays 4
  (the "tail" effect, mirroring web's `border-bottom-left-radius: 4px`).
  Background switched from surfaceContainerHighest (Slate) to surface
  (Iron) per the doc spec "card surface".
- Assistant bubble glow shadow added — accent-tinted blur (28px alpha
  0.14) + depth shadow (8px alpha 0.4 black). Mirrors web's
  --color-bubble-asst-shadow.

ActionColors wiring (Hybrid rule)
- 5 'Delete' confirm buttons across notes / tasks / chat conversations
  / calendar event sheet → Oxblood action-destructive via the
  ActionColors ThemeExtension defined in the foundation port. Foreground
  for ghost/text variants, backgroundColor for filled.
- Calendar event Save button → Moss action-primary. The first call
  site to wire ActionColors.primary; serves as the pattern for future
  Save reclassifications.
- Other Save buttons (note edit, task edit, project edit, etc.) still
  flow through colorScheme.primary (dusty violet) and read as
  brand-moment. Reclassifying those is deferred — the wiring pattern
  is established and can be applied incrementally as files are touched.

Indigo cleanup
- 4 hardcoded #7C3AED / #5B21B6 literals → dusty-violet equivalents
  (#5B4A8A / #3F3560). Spots: project_tasks_screen color fallback
  (×2), journal_screen gradient.

Verification
- flutter analyze: No issues found

What's deferred
- Per-screen Save / Cancel reclassification beyond the calendar event
  Save button. Wiring pattern established; rollout opportunistic.
- Long-form 1.7 line-height on assistant Markdown content (would
  require MarkdownStyleSheet work; minor).
- Surface walk on Knowledge / Projects / Settings screens for any
  hardcoded styling that needs touch.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

lib/screens/journal/journal_history_screen.dart

@@ -1,4 +1,5 @@
 import 'package:flutter/material.dart';
+import 'package:lucide_icons/lucide_icons.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 
 import '../../data/models/journal_day.dart';
@@ -27,9 +28,9 @@ class JournalHistoryScreen extends ConsumerWidget {
             itemBuilder: (context, i) {
               final isoDate = days[i];
               return ListTile(
-                leading: const Icon(Icons.menu_book_outlined),
+                leading: const Icon(LucideIcons.bookOpen),
                 title: Text(isoDate),
-                trailing: const Icon(Icons.chevron_right),
+                trailing: const Icon(LucideIcons.chevronRight),
                 onTap: () => Navigator.of(context).push(
                   MaterialPageRoute(
                     builder: (_) => _JournalDayDetailScreen(isoDate: isoDate),

lib/screens/journal/journal_screen.dart

@@ -1,6 +1,7 @@
 import 'dart:async';
 
 import 'package:flutter/material.dart';
+import 'package:lucide_icons/lucide_icons.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 
 import '../../core/exceptions.dart';
@@ -188,7 +189,7 @@ class _JournalScreenState extends ConsumerState<JournalScreen>
             )
           else
             IconButton(
-              icon: const Icon(Icons.refresh_outlined),
+              icon: const Icon(LucideIcons.refreshCw),
               tooltip: 'Regenerate prep',
               onPressed: _refresh,
             ),
@@ -426,7 +427,7 @@ class _GradientSendButton extends StatelessWidget {
             : const LinearGradient(
                 begin: Alignment.topLeft,
                 end: Alignment.bottomRight,
-                colors: [Color(0xFF7C3AED), Color(0xFF5B21B6)],
+                colors: [Color(0xFF5B4A8A), Color(0xFF3F3560)],
               ),
         color: disabled ? scheme.onSurface.withValues(alpha: 0.12) : null,
         borderRadius: BorderRadius.circular(10),
@@ -442,7 +443,7 @@ class _GradientSendButton extends StatelessWidget {
                 ),
               )
             : Icon(
-                Icons.send,
+                LucideIcons.send,
                 color: disabled
                     ? scheme.onSurface.withValues(alpha: 0.38)
                     : Colors.white,