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/knowledge/knowledge_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 'package:go_router/go_router.dart';
 
@@ -95,7 +96,7 @@ class _KnowledgeScreenState extends ConsumerState<KnowledgeScreen>
             : const Text('Knowledge'),
         actions: [
           IconButton(
-            icon: Icon(_searchActive ? Icons.close : Icons.search),
+            icon: Icon(_searchActive ? LucideIcons.x : LucideIcons.search),
             onPressed: () {
               setState(() => _searchActive = !_searchActive);
               if (!_searchActive) {
@@ -149,7 +150,7 @@ class _KnowledgeScreenState extends ConsumerState<KnowledgeScreen>
       floatingActionButton: FloatingActionButton(
         onPressed: () => _onFabTapped(context),
         tooltip: 'New',
-        child: const Icon(Icons.edit_outlined),
+        child: const Icon(LucideIcons.pencil),
       ),
     );
   }
@@ -259,7 +260,7 @@ class _KnowledgeScreenState extends ConsumerState<KnowledgeScreen>
           mainAxisSize: MainAxisSize.min,
           children: [
             _TypePickerRow(
-              icon: Icons.description_outlined,
+              icon: LucideIcons.fileText,
               label: 'Note',
               description: 'General note or document',
               onTap: () {
@@ -268,7 +269,7 @@ class _KnowledgeScreenState extends ConsumerState<KnowledgeScreen>
               },
             ),
             _TypePickerRow(
-              icon: Icons.person_outlined,
+              icon: LucideIcons.user,
               label: 'Person',
               description: 'Contact, colleague, or reference person',
               onTap: () {
@@ -277,7 +278,7 @@ class _KnowledgeScreenState extends ConsumerState<KnowledgeScreen>
               },
             ),
             _TypePickerRow(
-              icon: Icons.place_outlined,
+              icon: LucideIcons.mapPin,
               label: 'Place',
               description: 'Location, venue, or place of interest',
               onTap: () {
@@ -286,7 +287,7 @@ class _KnowledgeScreenState extends ConsumerState<KnowledgeScreen>
               },
             ),
             _TypePickerRow(
-              icon: Icons.checklist_outlined,
+              icon: LucideIcons.listChecks,
               label: 'List',
               description: 'Checklist or structured list',
               onTap: () {