Refactor nameplate cast tracking to be fully GUID-based

Problem:
Since a recent Turtle-WoW update, nameplates would show the same castbar on all mobs sharing a name (e.g. multiple "Defias Rogue Wizard"). Additionally, a targeted mob that was not casting would incorrectly display the castbar of a nearby mob with the same name.

Changes:
**`modules/nameplates.lua`**
- Removed `hasNampower` version-sniffing entirely. Nampower is a hard requirement for pfUI; all related guards have been removed and the code runs unconditionally.
- Castbar lookup now always uses `nameplate.cachedGuid` directly — never `GetUnitGUID("target")` or a unit name string.
- Removed dead fallback block using `UnitCastingInfo("target")`.
- Restored fallback via `pfGetCastInfo(cachedGuid)` / `pfGetChannelInfo(cachedGuid)` (see libcast changes below) for casts not tracked by libdebuff (e.g. already-in-progress casts on login).

**`libs/libcast.lua`**
- Renamed `UnitCastingInfo` → `pfGetCastInfo` and `UnitChannelInfo` → `pfGetChannelInfo` to avoid confusion with the Blizzard API of the same name, which does not exist in Vanilla.
- Name-based fallback lookup (`libcast.db[unitName]`) is now skipped when a GUID is available. This prevents cast bleed between mobs that share a name.

**`libs/libpredict.lua`, `modules/castbar.lua`, `modules/afkcam.lua`**
- Updated all call sites to use the renamed `pfGetCastInfo` / `pfGetChannelInfo`.

libs/libcast.lua

@@ -4,10 +4,10 @@ setfenv(1, pfUI:GetEnvironment())
 --[[ libcast ]]--
 -- A pfUI library that detects and saves all ongoing castbars of players, NPCs and enemies.
 -- The library also includes spells that usually don't have a castbar like Multi-Shot and Aimed Shot.
--- This is exclusivly used for vanilla in order to provide UnitChannelInfo and UnitCastingInfo functions.
+-- This is exclusivly used for vanilla in order to provide pfGetChannelInfo and pfGetCastInfo functions.
 --
 -- External functions:
---   UnitChannelInfo(unit)
+--   pfGetChannelInfo(unit)
 --     Returns information on the spell currently cast by the specified unit.
 --     Returns nil if no spell is being cast.
 --
@@ -19,7 +19,7 @@ setfenv(1, pfUI:GetEnvironment())
 --     endTime[Number] - Specifies when casting will end, in milliseconds.
 --     isTradeSkill[Boolean] - (DUMMY) Specifies if the cast is a tradeskill
 --
---   UnitCastingInfo(unit)
+--   pfGetCastInfo(unit)
 --     Returns information on the spell currently channeled by the specified unit.
 --     Returns nil if no spell is being channeled.
 --
@@ -53,7 +53,7 @@ local scanner = libtipscan:GetScanner("libcast")
 local libcast = CreateFrame("Frame", "pfEnemyCast")
 local player = UnitName("player")
 
-UnitChannelInfo = function(unit)
+pfGetChannelInfo = function(unit)
   -- convert to name if unitstring was given
   local unitName = pfValidUnits[unit] and UnitName(unit) or unit
   
@@ -117,7 +117,8 @@ UnitChannelInfo = function(unit)
   end
   
   -- Fallback to name-based lookup (CHAT_MSG castbars)
-  if not db and libcast.db[unitName] then
+  -- Skip when GUID is available to avoid same-name mob bleed
+  if not db and not guid and libcast.db[unitName] then
     db = libcast.db[unitName]
   end
   
@@ -145,7 +146,7 @@ UnitChannelInfo = function(unit)
   return cast, nameSubtext, text, texture, startTime, endTime, isTradeSkill
 end
 
-UnitCastingInfo = function(unit)
+pfGetCastInfo = function(unit)
   -- convert to name if unitstring was given
   local unitName = pfValidUnits[unit] and UnitName(unit) or unit
   
@@ -209,7 +210,8 @@ UnitCastingInfo = function(unit)
   end
   
   -- Fallback to name-based lookup (CHAT_MSG castbars)
-  if not db and libcast.db[unitName] then
+  -- Skip when GUID is available to avoid same-name mob bleed
+  if not db and not guid and libcast.db[unitName] then
     db = libcast.db[unitName]
   end
   
@@ -533,7 +535,7 @@ local function CastCustom(id, bookType, rawSpellName, rank, texture, castingTime
   local func = libcast.customcast[strlower(rawSpellName)]
   if not func then return end
 
-  if GetSpellCooldown(id, bookType) == 0 or UnitCastingInfo(player) then return end -- detect casting
+  if GetSpellCooldown(id, bookType) == 0 or pfGetCastInfo(player) then return end -- detect casting
 
   func(true)
 end