add rotation assist highlighting on CDM and action bars, as well as a dedicated rotation assist icon

[zol-wow]

Summary

• Add Rotation Assist system to uCDM, powered by Blizzard's C_AssistedCombat API, with three independent features: CDM icon highlighting, action bar highlighting, and a standalone button
• CDM Highlight draws a colored overlay on Essential/Utility viewer icons matching the next recommended spell, with per-viewer enable, color, style, and thickness settings
• Action Bar Highlight draws a colored overlay on action bar buttons (Blizzard, Bartender4, Dominos, ElvUI) matching the next recommended spell
• Standalone Button shows a movable icon with the next spell's texture, GCD swipe animation, keybind text, and configurable visibility (always / combat / hostile target)
• Both CDM and Action Bar highlights support two display styles: "Border" (4-edge inner border) and "Glow" (semi-transparent color fill across the entire icon)
• All three features share a single adaptive ticker (0.1s in combat, 0.25s idle) and are fully configurable under /tui > Cooldown Manager > Rotation Assist

Test plan

• /reload and open /tui > Cooldown Manager > Rotation Assist
• Enable CDM Highlight for Essential viewer, verify matching CDM icons get a colored border when the assist API suggests a spell
• Switch Essential highlight style to "Glow", verify the icon gets a semi-transparent color fill instead of a border
• Switch back to "Border", verify it reverts to the 4-edge border
• Verify the thickness slider is disabled when style is "Glow" and re-enables when switching back to "Border"
• Repeat the above for Utility viewer
• Enable Action Bar Highlight, verify matching action bar buttons get highlighted
• Test Action Bar style toggle between "Border" and "Glow"
• Verify color picker affects both styles correctly
• Enable the Standalone Button, verify it shows the next spell icon
• Verify GCD swipe, keybind text, visibility modes, drag-to-move (unlock), and reset position all work
• Verify all features deactivate cleanly when disabled
• Profile switch: verify highlights reset and re-apply correctly