feat: add model selection for remote transcription

[AzimovS]

Summary

• Add a dedicated endpointUrl column to transcript_settings, separating endpoint URL from model name (previously overloaded in the model column for remote providers)
• Remote transcription settings UI now shows three fields: Endpoint URL, Model Name, and API Key
• Model name is sent as the model parameter in the multipart form to OpenAI-compatible transcription endpoints
• Fixes pre-existing bug where TranscriptSetting struct was missing the runpodApiKey field

Key Design Decisions

• Two-phase migration: URL kept in both model and endpointUrl columns for safe rollback. Rust code reads endpointUrl first with fallback to model
• Conditional model sending: model form parameter only sent when non-empty (some self-hosted servers don't expect it)
• Input validation: Model name limited to 256 chars, no control characters. URL sanitized in logs (query params stripped)
• Migrated data safety: resolve_remote_params() detects when model equals the URL (migrated data) and treats it as empty to avoid sending URL as the model name

Test plan

• Save remote transcription config with all three fields, navigate away and back -- all fields persist
• Switch from remote to parakeet and back -- remote fields restored
• Fresh install defaults to parakeet with no errors
• Existing remote config users: URL migrated to endpointUrl, transcription still works
• cargo check passes
• pnpm run build passes

🤖 Generated with Claude Code

[AzimovS]

Code review

No issues found. Checked for bugs and CLAUDE.md compliance.

Reviewed areas:

• SQLite migration pattern (table-recreation, PRAGMA usage, data transformation)
• Rust structs and repository layer (TranscriptSetting, save/get methods)
• Remote provider model validation and multipart form handling
• Frontend state management (TranscriptSettings, ConfigContext, Sidebar)
• All callers of api_save_transcript_config pass endpointUrl

🤖 Generated with Claude Code

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