Convert the default conversation id to a uuid, plus other fixes (#918)

* Update the conversation_id primary key field to be a uuid

- update associated API endpoints
- this is to improve the overall application health, by obfuscating some information about the internal database
- conversation_id type is now implicitly a string, rather than an int
- ensure automations are also migrated in place, such that the conversation_ids they're pointing to are now mapped to the new IDs

* Update client-side API calls to correctly query with a string field

* Allow modifying of conversation properties from the chat title

* Improve drag and drop file experience for chat input area

* Use a phosphor icon for the copy to clipboard experience for code snippets

* Update conversation_id parameter to be a str type

* If django_apscheduler is not in the environment, skip the migration script

* Fix create automation flow by storing conversation id as string

The new UUID used for conversation id can't be directly serialized.
Convert to string for serializing it for later execution

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Co-authored-by: Debanjum Singh Solanky <debanjum@gmail.com>

src/khoj/database/models/__init__.py

@@ -350,6 +350,7 @@ class Conversation(BaseModel):
     title = models.CharField(max_length=200, default=None, null=True, blank=True)
     agent = models.ForeignKey(Agent, on_delete=models.SET_NULL, default=None, null=True, blank=True)
     file_filters = models.JSONField(default=list)
+    id = models.UUIDField(default=uuid.uuid4, editable=False, unique=True, primary_key=True, db_index=True)
 
 
 class PublicConversation(BaseModel):