Modernize frontend with tabs, HTMX, and Tailwind build pipeline

Complete UI overhaul implementing modern design patterns with HTMX for
dynamic updates, proper Tailwind build pipeline, and improved UX.

Build Pipeline:
- Add npm + PostCSS + Tailwind CSS configuration
- Custom design system with brand colors
- Compiled CSS: 27KB (vs 3MB CDN), 99% reduction
- Makefile for unified build commands
- Inter font for improved typography

Tab Interface:
- Separate Tasks tab from Notes tab using HTMX
- Partial page updates without full refreshes
- Tab state management with proper refresh handling
- New endpoints: /tabs/tasks, /tabs/notes, /tabs/refresh

Template Architecture:
- Modular partials system (7 reusable components)
- Cleaner separation of concerns

Empty Board Management:
- Active boards in main 3-column grid
- Empty boards in collapsible section
- Reduces visual clutter

Visual Design Enhancements:
- Inter font, brand color accents
- Improved typography hierarchy and spacing
- Enhanced card styling with hover effects

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

1 files changed, 37 insertions, 1 deletions

diff --git a/SESSION_STATE.md b/SESSION_STATE.md
index 55138c9..f4b76f0 100644
--- a/SESSION_STATE.md
+++ b/SESSION_STATE.md
@@ -1,7 +1,7 @@
 # Current Session State
 
 ## 🎯 Active Goal
-Board sorting implementation complete.
+Frontend modernization with tabs, HTMX, and Tailwind build pipeline complete.
 
 ## ✅ Completed
 - Initial Phase 1 feature set (Trello, Todoist, Obsidian, PlanToEat)
@@ -30,12 +30,48 @@ Board sorting implementation complete.
   - internal/api/trello.go:220-228: Added sort logic to GetBoardsWithCards
   - internal/store/sqlite.go:428-433: Updated SQL query to sort cached boards consistently
   - Empty boards now pushed to bottom, active boards at top
+  - **Commit:** 9ef5b7f "Sort Trello boards with active boards first"
+- **Frontend Modernization:** Complete UI overhaul with tabs, HTMX, and Tailwind build pipeline
+  - **Build Pipeline:** npm + PostCSS + Tailwind configuration (replaced CDN)
+    - package.json, tailwind.config.js, postcss.config.js, Makefile
+    - Custom design system with brand colors (Trello, Todoist, Obsidian, PlanToEat)
+    - Compiled CSS: 27KB (vs 3MB CDN), Inter font, custom components
+  - **Tab Interface:** Separate "Tasks" (Trello/Todoist/PlanToEat) from "Notes" (Obsidian)
+    - HTMX for partial page updates (no full refreshes)
+    - Tab switching with proper state management
+    - Auto-refresh maintains current tab context
+  - **Template Restructuring:** Modular partials architecture
+    - web/templates/partials/: 7 reusable template components
+    - tasks-tab.html, notes-tab.html, trello-boards.html, todoist-tasks.html, etc.
+    - Cleaner separation of concerns
+  - **Empty Board Collapsible:** Native `<details>` accordion for empty Trello boards
+    - Active boards displayed prominently in 3-column grid
+    - Empty boards hidden in expandable section
+    - Reduces visual clutter, scales well
+  - **Backend Tab Endpoints:** HTMX-compatible handlers
+    - /tabs/tasks, /tabs/notes, /tabs/refresh routes
+    - HandleTasksTab, HandleNotesTab, HandleRefreshTab methods
+    - Selective rendering for faster tab switches
+  - **JavaScript Enhancements:** app.js rewritten for HTMX integration
+    - HTMX event listeners for loading states
+    - Current tab tracking for refresh/auto-refresh
+    - Improved error handling
+  - **Visual Design:** Modern aesthetic with brand colors
+    - Section headers with color-coded accents
+    - Improved typography hierarchy (Inter font)
+    - Enhanced spacing (10-unit sections, 6-unit cards)
+    - Card hover effects with smooth transitions
+    - Custom scrollbar styling
 
 ## 🏗️ Architecture & Decisions
 - **Decision:** Use SQLite for caching with a 5-minute TTL.
 - **Decision:** Trello is the primary task system, requiring Key+Token auth.
 - **Decision:** Limit Trello concurrent requests to 5 to prevent API rate limiting.
 - **Decision:** Removed AI agent endpoint - dashboard is human-facing only.
+- **Decision:** HTMX over React/Vue for simpler state management and server-side rendering.
+- **Decision:** Compiled Tailwind over CDN for 99% smaller CSS and custom design tokens.
+- **Decision:** Template partials for HTMX-friendly swap targets and reusability.
+- **Decision:** Native `<details>` element for empty board collapsible (no JS required).
 
 ## 📋 Next Steps
 1. **Future:** Consider Phase 2 features (write operations, user management).