feat: add inline timestamps STT output format

[brittain9]

Summary

Adds a new Inline Timestamps text format option for speech-to-text output, allowing timestamps to be embedded directly within transcribed text as an alternative to SRT subtitle format.

Closes #222

Screenshots

Note: the TTS output at the bottom that strips the current timestamp template.

Motivation

When transcribing audio (podcasts, meetings, interviews), I want timestamps inline with text for:

• Easier human readability vs. SRT's rigid block format
• LLM post-processing (summarization, Q&A) where inline context is more natural
• Quick reference without the overhead of subtitle parsing

Changes

New Settings (Settings → Speech to Text)

Setting	Description
Text format	New "Inline Timestamps" option
Timestamp template	Customizable format with {hh}, {mm}, {ss}, {ms}, {text} tokens
Minimum interval	Prevents timestamp spam

Example output: [00:05] Hello world [00:12] This is a test

Implementation

• text_tools.cpp: Core functions for formatting, regex compilation, and stripping timestamps
• STT Engines: Integrated into Vosk, Whisper, FasterWhisper, April, and DeepSpeech
• TTS Integration: Auto-strips inline timestamps before speaking (seamless text-to-speech of transcribed content)
• Bug fix: Corrected text format resetting to "Plain Text" when clearing notepad

Tests

• Unit tests covering format_segments_inline, compile_inline_timestamp_regex, strip_inline_timestamps
• Edge cases: interval state across batches, complex template formats, whitespace handling

Testing Done

• Unit tests pass (text_tools_test)
• Manual testing with Vosk, April, Whisper engine
• TTS strips timestamps before speaking
• Settings UI functional with presets and custom templates

[mkiol]

Sorry for late reply. It looks fantastic :)

I'm a bit busy at the moment and need a few more days to look at the code and test it. Thank you for your understanding.