fix: reject empty guild id in oauth authorization

[karmugilan28]

What the issue was

The OAuth2 authorization endpoint accepted an empty string ("") for guild_id because the schema definition (ApplicationAuthorizeSchema) lacked a minimum length constraint.

What was changed

• Added the @minLength 1 JSDoc validation rule to the guild_id property in src/schemas/uncategorised/ApplicationAuthorizeSchema.ts.
• Regenerated the runtime JSON schemas using npm run generate:schema to apply the constraint to AJV.
• Removed the stale // TODO: ensure guild_id is not an empty string comment from src/api/routes/oauth2/authorize.ts since the route wrapper middleware now intercepts and rejects empty strings automatically.

Addresses the specific TODO from #1600.

[TheArcaneBrony]

Question: was this PR AI-generated or -assisted?

[karmugilan28]

Sir this PR is not AI generated . This is done with the ai-assisted and not completely AI-based

[FoxofWinter]

Sir this PR is not AI generated . This is done with the ai-assisted and not completely AI-based

"Keep in mind that we do, under no circumstances, accept AI-generated, AI-assisted, or otherwise machine-generated contributions, for legal reasons." https://github.com/spacebarchat/server/blob/master/CONTRIBUTING.MD
Spacebar does not accept any AI-assisted contributions.