Update changelog and welcome page for v2.13.1

Add missing entries for v2.12.1, v2.13.0, and v2.13.1 to
CHANGELOG.md. Update config.py CHANGELOG highlights to reflect
UI overhaul, signal scanner rewrite, and WiFi client fix.

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

CHANGELOG.md

@@ -2,6 +2,68 @@
 
 All notable changes to iNTERCEPT will be documented in this file.
 
+## [2.13.1] - 2026-02-04
+
+### Added
+- **UI Overhaul** - Revamped styling with slate/cyan theme
+  - Switched app font to JetBrains Mono
+  - Global navigation bar across all dashboards
+  - Cyan-tinted map tiles as default
+- **Signal Scanner Rewrite** - Switched to rtl_power sweep for better coverage
+  - SNR column added to signal hits table
+  - SNR threshold control for power scan
+  - Improved sweep progress tracking and stability
+  - Frequency-based sweep display with range syncing
+- **Listening Post Audio** - WAV streaming with retry and fallback
+  - WebSocket audio fallback for listening
+  - User-initiated audio play prompt
+  - Audio pipeline restart for fresh stream headers
+
+### Fixed
+- WiFi connected clients panel now filters to selected AP instead of showing all clients
+- USB device contention when starting audio pipeline
+- Dual scrollbar issue on main dashboard
+- Controls bar alignment in dashboard pages
+- Mode query routing from dashboard nav
+
+---
+
+## [2.13.0] - 2026-02-04
+
+### Added
+- **WiFi Client Display** - Connected clients shown in AP detail drawer
+  - Real-time client updates via SSE streaming
+  - Probed SSID badges for connected clients
+  - Signal strength indicators and vendor identification
+- **Help Modal** - Keyboard shortcuts reference system
+- **Main Dashboard Button** - Quick navigation from any page
+- **Settings Modal** - Accessible from all dashboards
+
+### Changed
+- Dashboard CSS improvements and consistency fixes
+
+---
+
+## [2.12.1] - 2026-02-02
+
+### Added
+- **SDR Device Registry** - Prevents decoder conflicts between concurrent modes
+- **SDR Device Status Panel** - Shows connected SDR devices with ADS-B Bias-T toggle
+- **Real-time Doppler Tracking** - ISS SSTV reception with Doppler correction
+- **TCP Connection Support** - Meshtastic devices connectable over TCP
+- **Shared Observer Location** - Configurable shared location with auto-start options
+- **slowrx Source Build** - Fallback build for Debian/Ubuntu
+
+### Fixed
+- SDR device type not synced on page refresh
+- Meshtastic connection type not restored on page refresh
+- WiFi deep scan polling on agent with normalized scan_type value
+- Auto-detect RTL-SDR drivers and blacklist instead of prompting
+- TPMS pressure field mappings for 433MHz sensor display
+- Agent capabilities cache invalidation after monitor mode toggle
+
+---
+
 ## [2.12.0] - 2026-01-29
 
 ### Added