SnapHeal: Click-Cast Healing

## Added
- Keyboard click-casting: bind any keyboard key (not just mouse buttons) to cast a heal spell on whichever unit frame is under your mouse.
- Keyboard casting now auto-detects whether the running client supports it, based on client version - enabled by default, automatically disabled on WoW Forever Beta's current version track (which doesn't yet expose the required binding API to secure snippets). A single addon file now works correctly for both Midnight/Retail and WoW Forever Beta.
- New /shshow and /shhide commands to show/hide the entire addon (frame + anchor).
- New "About" page in the config window (bottom of the category list): shows addon name, version and author (read from the .toc), plus a copyable link to the CurseForge page.
- Minimap icon now supports three actions: left-click opens the config window, middle-click shows/hides the addon, right-click locks/unlocks the anchor.
- A bold warning is now shown on the Keybinds page, and in the key-capture popup, whenever keyboard casting is disabled for the current client.

## Changed
- All slash commands are now dedicated, single-word commands instead of "/sh <subcommand>": /shconfig, /shlock, /shunlock, /shreset (plus the new /shshow/ /shhide). Running bare /sh still prints a help overview.
- Renamed the debug command /hhscan to /shscan for consistent naming.
- All debug/diagnostic command output (/shpower, /shrange, /shcast, /shscan) is now in English. /shcast also prints the client's version/build and whether keyboard casting is enabled for it.
- Default settings changed: health text now shows as a percentage by default, and the resource bar now defaults to showing all active resources instead of mana only.
- The anchor now displays "Group" instead of "SnapHeal" as its label.
- Registered the CurseForge project ID in the .toc for the CurseForge updater.

## Fixed
- Fixed a Lua error ("attempt to call a nil value") that occurred on every unit frame hover in the WoW Forever Beta, caused by that client not exposing the secure key-binding API used for keyboard casting.

## Removed
- Removed the "Loaded successfully" chat message on login.