feat(ui): implement premium gamified Concepts Map dashboard, unify design tokens, and enforce scoped CSS (#54)

Resolves #55

# gamified Concepts Map Dashboard, Architecture Cleanup, & CSS Unification

This Pull Request completes the gamified **Concepts Map** interactive experience and executes a strict visual and architectural clean-up of the **NexusReader SaaS** platform by consolidating styling around the centralized **Nexus Neon** design system, enforcing Native AOT-compliant scoped-CSS, and resolving style drift.

---

### 🚀 Key Implementations

#### 1. Gamified Interactive Concepts Map Dashboard
* **Dynamic Skill-Tree Visualizer:** Implemented a gamified node-based interactive tree that reads concept connections dynamically, rendering progress nodes, unlocked/locked states, and active visual connection lines.
* **Premium UX Details:** Integrated high-fidelity hover effects, detailed sidebar popovers showing unlocked stats/summaries, and smooth parallax backdrops.
* **Secure Multi-Tenant Gating:** Hardened data queries using explicit `TenantId` gating to ensure complete layout isolation between system tenants.

#### 2. Architecture & Service Optimization
* **Service Abstraction (`IConceptsMapService`):** Introduced a clean service interface decoupled from the UI layers.
* **Polyglot Fallback Implementations:**
  - **WasmConceptsMapService:** Implements efficient client-side fetching with error recovery/loading states.
  - **ServerConceptsMapService:** Handles deep database graph mapping, relationship resolution, and multi-tenant checks.
* **CQRS Integrity:** Enforced the CQRS Result Pattern by using `MediatR` handlers to fetch data structures instead of placing database queries in UI modules.

#### 3. Nexus Neon CSS Unification & Zero-Style-Tag Standards
* **Central Design Tokens:** Solidified typography (`Inter` / `Merriweather`), primary brand green hues (`var(--nexus-neon)` at `#00ff99`), and glow variables inside the global `app.css`.
* **Zero Inline Style Tags:** Standardized all dashboard modules by completely eliminating inline `<style>` blocks in favor of scoped `.razor.css` companion files.
* **Consolidated Buttons & Glass Panels:**
  - Standardized `.btn-nexus`, `.btn-nexus-primary`, and `.btn-nexus-secondary` throughout header/footer/card operations.
  - Removed duplicate `.glass-panel` background, blur, and support-declaration overrides, making components cleanly inherit standard global styles.
* **Eliminated Brand Splitting:** Resolved legacy purple-indigo user avatar and conversation bubble gradients inside the AI Intelligence Hub (`Intelligence.razor.css`), migrating them to premium glassmorphic surfaces (`rgba(255, 255, 255, 0.05)`) contrasting beautifully against the emerald green AI theme.

---

### 🧪 Verification & Build Gate Status

* **Successful Compilation Check:** Run `dotnet build NexusReader.slnx --no-restore` from the workspace root. Flawlessly succeeded with **zero compilation errors** (`Liczba błędów: 0`) under target `.NET 10`.
* **Verified Skills Synchrony:** The companion design guidelines skill (`nexus-ui-engine/SKILL.md`) has been fully updated to secure these layout and styling conventions for future dashboard features.

---------

Co-authored-by: Marek Jasiński <jasins.marek@gmail.com>
Reviewed-on: #54
Co-authored-by: Antigravity <antigravity@google.com>
Co-committed-by: Antigravity <antigravity@google.com>

.agent/skills/nexus-ui-engine/SKILL.md

@@ -12,14 +12,22 @@ description: Design System & Component rules for Blazor
 
 - **Styling & Isolation:** 
   - Mandatory use of scoped CSS (`.razor.css`).
+  - Strict compliance: Zero inline `<style>` tags are allowed in `.razor` files.
   - No global CSS except for design tokens in `app.css`.
   - Use `::deep` only when absolutely necessary to style child components.
 
 - **Design System (Nexus Neon):**
   - **Color Palette:**
     - Primary Accent: `--nexus-neon` (`#00ff99`) - Used for borders, highlights, and icons.
+    - Neon Glow: `--nexus-neon-glow` / `--nexus-primary-glow` (`rgba(0, 255, 153, 0.3)`).
     - Dark Mode: `--nexus-bg` (`#0a0a0a`), `--nexus-card` (`#141414`).
     - Light Mode: `--nexus-bg` (`#f8f9fa`), `--nexus-card` (`#ffffff`).
+    - **No Brand Splitting:** Strict ban on custom purple/indigo/cyan elements or hardcoded accent colors (like `#7c3aed`, `#4c1d95`, `#00b3ff`) on dashboard pages. Neutral/glass surfaces (`rgba(255, 255, 255, 0.05)`) must be used for secondary elements to preserve contrast and ensure the AI/neon-green elements are the focal point.
+  - **Buttons:**
+    - Must inherit from the global `.btn-nexus` class in `app.css`.
+    - Primary Button: `.btn-nexus-primary` (background: `var(--nexus-neon)`, text color: `#000`).
+    - Secondary Button: `.btn-nexus-secondary` (background: `rgba(255, 255, 255, 0.05)`, border: `1px solid rgba(255, 255, 255, 0.1)`, text color: `#fff`).
+    - Hover Interaction: `transform: translateY(-2px)`, increased brightness, and a signature primary neon glow shadow.
   - **Typography:**
     - UI Elements: `Inter` (Sans-Serif) for controls, menus, and labels.
     - Reading Content: `Merriweather` (Serif) with `line-height: 1.65` and `letter-spacing: -0.01em` for high readability.
@@ -44,6 +52,9 @@ description: Design System & Component rules for Blazor
 - **Interactive Flow:**
   - AI Assistant interactions must be non-blocking and smoothly transition using CSS animations.
   - Interactive elements must have clear `:hover`, `:active`, and `:focus` states.
-  - **Glass Panel Standard:** All primary data panels (`.glass-panel`) must implement the following interaction signature:
-    - `transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1)`
-    - `:hover` state must include: `transform: translateY(-4px)`, increased background opacity, and a subtle `--nexus-neon` border highlight (e.g., `rgba(0, 255, 153, 0.2)`).
+  - **Glass Panel Standard:** All primary data panels (`.glass-panel`) must implement the following global parameters from `app.css` (only local modifiers like padding and hover offsets should live in scoped CSS):
+    - Background: `rgba(20, 20, 20, 0.85)` (fallback) / `rgba(255, 255, 255, 0.03)` with `backdrop-filter: blur(10px)` when supported.
+    - Border: `1px solid rgba(255, 255, 255, 0.05)`.
+    - Border Radius: `var(--radius-xl)`.
+    - Transition: `all 0.3s cubic-bezier(0.4, 0, 0.2, 1)`.
+    - `:hover` state: `transform: translateY(-4px)` (or local offset) and highlight accent `border-color: rgba(0, 255, 153, 0.2)`.