fix: replace all hardcoded hex colors with CSS theme variables

Phase 15c — theme-consistent color system:

Replaced 63 instances of hardcoded hex colors (#5e6ad2, #7170ff, #4f46e5,
#6a75e0, #828fff, #94a3b8, etc.) with CSS variables from globals.css:
- #5e6ad2 → var(--brand) (light: #5e6ad2, dark: #5e6ad2)
- #7170ff → var(--accent) (light: #4f46e5, dark: #7170ff)
- #4f46e5 → var(--accent)
- #6a75e0 → var(--brand-hover) (new var, light: #6a75e0, dark: #7170ff)
- #828fff → var(--accent-hover)
- #868686 → var(--text-dim)
- Dark-mode-specific hex in Markdown.tsx → CSS variables

Added --brand-hover CSS variable (light: #6a75e0, dark: #7170ff)
Added dark:prose-invert instead of prose-invert (light mode now uses
default prose theme instead of forced dark)

Files changed: 15 component files + globals.css

.hermes/plans/theme-colors.md

@@ -0,0 +1,43 @@
+# Phase 15c — Theme-Consistent Color System
+
+> User: "banyak pewarnaan yg tidak sesuai tema dark mode atau light mode"
+
+## Problem
+63 hardcoded hex colors (#5e6ad2, #7170ff, #4f46e5, etc.) bypass the CSS
+variable theme system in globals.css. These don't adapt between light/dark mode
+properly — the `dark:` variant changes text color but background stays the same.
+
+## Color Mapping
+
+### `#5e6ad2` (indigo-600)
+- Light: `--brand: #5e6ad2` (same)
+- Dark: `--brand: #5e6ad2` (same)
+→ Replace with `var(--brand)`
+
+### `#4f46e5` (indigo-700)
+- Light: `--accent: #4f46e5`
+- Dark: `--accent: #7170ff`
+→ Replace with `var(--accent)`
+
+### `#7170ff` (light blue, dark mode accent)
+- Light: `var(--accent)` (#4f46e5)
+- Dark: `var(--accent)` (#7170ff)
+→ Replace `dark:text-[#7170ff]` → `dark:text-[var(--accent)]`
+
+### `#6a75e0` (hover lighter)
+→ Replace with `var(--accent-hover)`
+
+### `/10`, `/15`, `/20`, `/30` opacity tints
+- `bg-[#5e6ad2]/15` → `bg-[var(--brand)]/15`
+- `bg-[#5e6ad2]/10` → `bg-[var(--brand)]/10`
+- `bg-[#5e6ad2]/30` → `bg-[var(--brand)]/30`
+
+## Files to fix
+- `[section]/[...slug]/page.tsx` (~16 instances)
+- `[section]/page.tsx` (~5 instances)
+- `components/Sidebar.tsx` (2 instances)
+- `components/DocForm.tsx` (~6 instances)
+- `components/CommandMenu.tsx` (~6 instances)
+- `components/Header.tsx` (2 instances)
+- `components/McpConfigSnippet.tsx` (1 instance)
+- `page.tsx` (check)