fix: add missing signal invocations in Bot.tsx

[SyncWithRaj]

Fixed logic errors in Bot.tsx where Solid.js signal accessors were being checked as function references instead of being invoked. In Solid.js, signals are functions; referencing them without () evaluates to truthy (the function itself), causing conditional guards to fail.

Key Fixes

• Voice Recording: Fixed onRecordingCancelled to correctly invoke recordingNotSupported(). This ensures cancelAudioRecording() is called, preventing the microphone from staying active after a user cancels.
• Drag & Drop: Fixed handleDrop to correctly invoke isFileUploadAllowed(), ensuring that file upload permissions are strictly enforced during drop events.

Impact

• Fixes a privacy concern where the recording indicator remained active in the browser after cancellation.
• Resolves a bypass in file upload gating for drag-and-drop interactions.

[gemini-code-assist]

Code Review

This pull request corrects the logic in Bot.tsx by properly invoking isFileUploadAllowed and recordingNotSupported as functions. A review comment identifies a functional issue in the handleDrop handler where an early return prevents e.preventDefault() from executing, which could lead to unintended browser navigation when uploads are disabled.