feat: in-game options panel with per-alert sound picker (#6)

[lemillermicrosoft]

Closes #6. Replaces the previously-stacked PR #7 (its base branch was deleted when #8 shipped v0.3.0).

Requested by deehoc via Discord DM:

User should be able to select which sound is used for different alerts in a nice config UI. in-game addon options would be a good way to do this, too.

What lands

• New Options.lua module registered via InterfaceOptions_AddCategory (TBC 2.5.6 API). Reachable via ESC → Interface → AddOns → BlasterMaster, or /blaster options (alias /blaster config).
• Per-alert sound dropdown for all 5 roles: Enter Combat (laser), Low HP Alarm (siren), Kill Jingle (oneUp), Level Up (fanfare), Crit (crit).
• Preview button next to each dropdown — plays the currently selected file via PlaySoundFile.
• Toggles for HUD enabled, Mute all sounds, Crit audio enabled.
• Slider for Low HP Threshold (5%–95%, 5% steps).
• Reset sounds button restores hardcoded defaults.
• playSFX in BlasterMaster.lua now consults BlasterMaster_GetSfxPath(role) first (reads BlasterMasterDB.sfxMap), falls back to the hardcoded SFX table.
• BlasterMasterDB.sfxMap persists per role → filename mapping.
• Post-class-agnostic crit rework (v0.3.0): dropped the critShadow role from the panel.

How it works

• Static file list: AUDIO_FILES[1..37] = "Blaster Master SFX (i).wav" — Lua can't ls, so this is baked in. If new files are added later, update AUDIO_FILES in Options.lua.
• Dropdowns label entries as SFX 1 .. SFX 37. Post-MVP: friendly names once we know what each sound is.

Not in this PR

• Volume slider per role (post-MVP — PlaySoundFile doesn't accept volume in this API).
• LibSharedMedia integration.
• Custom drag-and-drop of user files.
• Per-character options.

Ship with !ship blastermaster after smoke-testing that the panel opens and previews work.