feat: implement stage1 API

[TakalaWang]

This pull request includes significant changes to the src/lib and src/routes directories to update the data structures and enhance functionality for handling sessions and discussions. The most important changes include modifying the data structures for sessions, individual discussions, and group discussions, as well as adding new functions and endpoints to handle these changes.

Changes to data structures:

• src/lib/types/IndividualDiscussion.ts: Added goal, subQuestions, and resourcesTexts fields to FirestoreIndividualDiscussion and IndividualDiscussion interfaces. Updated convertFirestoreIndividualDiscussion to include these new fields. [1] [2] [3]
• src/lib/types/groupDiscussion.ts: Added groupName field to FirestoreGroupDiscussion and GroupDiscussion interfaces. Updated convertFirestoreGroupDiscussion to include this new field. [1] [2] [3]
• src/lib/types/session.ts: Added stage, resourceIds, and groups fields to FirestoreSession and Session interfaces. Updated convertFirestoreSession to include these new fields. [1] [2] [3]

Enhancements to functionality:

• src/routes/session/[id]/participant/+page.server.ts: Added new actions startIndividualStage and sendConversation to handle the start of the individual stage and sending conversations, respectively. (src/routes/session/[id]/participant/+page.server.tsR71-R156)
• src/routes/session/[id]/participant/+page.svelte: Updated the component to handle the new data structure for groups and participants. Removed the QR code functionality for group leaders. (src/routes/session/[id]/participant/+page.svelteL19-R18, src/routes/session/[id]/participant/+page.svelteL137-R147)

Refactoring and cleanup:

• src/lib/server/llm.ts: Refactored the Document interface to use name and text fields instead of title and content. Updated the chatWithLLMByDocs function accordingly. [1] [2] [3] [4]
• src/lib/types/speech.ts: Removed the FirestoreSpeech and Speech interfaces along with the convertFirestoreSpeech function.
• src/routes/session/[id]/+page.svelte: Removed the Link icon import and related conditional rendering for resource types. (src/routes/session/[id]/+page.svelteL11, src/routes/session/[id]/+page.svelteL216-R217)

New utility function:

• src/lib/server/parse.ts: Added a placeholder function parsePdf2Text to parse PDF files to text.