feat(ui): implement 'Twilight Velvet' dark theme and fix visibility issues

- Add 'Twilight Velvet' color palette to globals.css with OKLCH values
- Update SettingsPage headers, cards, and dialogs to use semantic theme variables
- Update HistoryCard, HistoryFeed, and DraftContent to support dark mode
- Update ProviderSelector and ProviderList to use custom card background (#2A2A3D)
- Add ThemeToggle component with improved visibility
- Ensure consistent use of 'bg-card', 'text-foreground', and 'text-muted-foreground'

_bmad-output/implementation-artifacts/sprint-status.yaml

@@ -1,6 +1,6 @@
-# generated: 2026-01-24
-# project: Test01
-# project_key: TEST01
+# generated: 2026-01-27
+# project: Brachnha Insights
+# project_key: BRACHNHA
 # tracking_system: file-system
 # story_location: /home/maximilienmao/Projects/Test01/_bmad-output/implementation-artifacts
 
@@ -33,41 +33,43 @@
 # - SM typically creates next story after previous one is 'done' to incorporate learnings
 # - Dev moves story to 'review', then runs code-review (fresh context, different LLM recommended)
 
-generated: 2026-01-24
-project: Test01
-project_key: TEST01
+generated: 2026-01-27
+project: Brachnha Insights
+project_key: BRACHNHA
 tracking_system: file-system
 story_location: /home/maximilienmao/Projects/Test01/_bmad-output/implementation-artifacts
 
 development_status:
-  # Epic 1: "Active Listening" - Core Chat & Teacher Agent
+  # Epic 1: Gatekeeper Security
   epic-1: done
-  1-1-local-first-setup-chat-storage: done
-  1-2-chat-interface-implementation: done
-  1-3-teacher-agent-logic-intent-detection: done
-  1-4-fast-track-mode: done
+  1-1-security-middleware-lock-screen: done
+  1-2-server-side-validation-app-password: done
+  1-3-session-persistence: done
   epic-1-retrospective: done
 
-  # Epic 2: "The Magic Mirror" - Ghostwriter & Draft Refinement
+  # Epic 2: Project Calibration
   epic-2: done
-  2-1-ghostwriter-agent-markdown-generation: done
-  2-2-draft-view-ui-the-slide-up: done
-  2-3-refinement-loop-regeneration: done
-  2-4-export-copy-actions: done
+  2-1-settings-feature-shell: done
+  2-2-provider-management-crud: done
+  2-3-secure-credentials-storage: done
+  2-4-connection-validation: done
+  2-5-active-provider-switcher: done
   epic-2-retrospective: done
 
-  # Epic 3: "My Legacy" - History, Offline Sync & PWA Polish
+  # Epic 3: The Venting Ritual
   epic-3: done
-  3-1-history-feed-ui: done
-  3-2-deletion-management: done
-  3-3-offline-sync-queue: done
-  3-4-pwa-install-prompt-manifest: done
-  epic-3-retrospective: optional
+  3-1-chat-interface-state: done
+  3-2-teacher-agent-elicitation-logic: done
+  3-3-ghostwriter-agent-draft-generation: done
+  3-4-draft-review-ui-slide-up: done
+  3-5-regeneration-loop-refinement: done
+  epic-3-retrospective: done
 
-  # Epic 4: "Power User Settings" - BYOD & Configuration
+  # Epic 4: Journey Management
   epic-4: done
-  4-1-api-provider-configuration-ui: done
-  4-2-connection-validation: done
-  4-3-model-selection-configuration: done
-  4-4-provider-switching: done
-  epic-4-retrospective: optional
+  4-1-history-feed-ui: done
+  4-2-detailed-artifact-view: done
+  4-3-action-menu-export-delete: done
+  4-4-offline-sync-queue: done
+  4-5-data-export-utility: done
+  epic-4-retrospective: done