Expose the proxy DLL rename as a user-selectable option across all
injection paths.  Previously hardcoded to dxgi.dll with no way to
change it short of manually prepending DLL=<name> to the Steam launch
option.

src/utils/constants.ts
- Add PROXY_DLL_OPTIONS (7 entries matching _create_renamed_copies)
  each with a label and one-line hint
- Add DEFAULT_PROXY_DLL constant (dxgi.dll) and ProxyDllValue type

src/api/index.ts
- runManualPatch now takes [directory, dll_name] so the chosen name
  reaches the backend

src/components/OptiScalerControls.tsx
- Own dllName state (default: dxgi.dll)
- Render a DropdownItem (visible when installed) showing the 7 options
  with the selected option's hint as the description
- Pass dllName down to both ClipboardCommands and ManualPatchControls

src/components/ClipboardCommands.tsx
- Accept dllName prop
- Patch command is plain ~/fgmod/fgmod %command% for the default;
  prefixed DLL=<name> ~/fgmod/fgmod %command% for any other choice

src/components/CustomPathOverride.tsx
- Accept dllName prop
- Pass it to runManualPatch
- Manual launch cmd clipboard button builds
  WINEDLLOVERRIDES="<stem>=n,b" dynamically; emits bare
  SteamDeck=0 %command% for OptiScaler.asi (ASI loader path needs no
  Wine DLL override)

main.py
- Add VALID_DLL_NAMES set (whitelist matching the renames dir)
- manual_patch_directory validates dll_name against the whitelist and
  returns an error for unknown values
- _manual_patch_directory_impl accepts dll_name param; removes the
  hardcoded "dxgi.dll" line

defaults/assets/fgmod.sh
- Fix longstanding bug: WINEDLLOVERRIDES was hardcoded to dxgi=n,b
  regardless of the DLL= env var selection.  Now derives the stem from
  $dll_name and skips the override entirely for .asi files.