fix(ai-phala): require clean api base urls

[aiirvizionz]

Summary

• validate Phala custom baseUrl values before building the chat completions URL
• reject invalid URLs, non-http(s) schemes, credentials, query strings, and fragments before any network request
• keep trailing slash normalization covered while adding unsafe custom base URL cases

Why

The adapter trimmed trailing slashes, but still accepted malformed or surprising custom API bases. This change makes Phala fail early with adapter-specific configuration errors instead of sending requests to unclear destinations.

Validation

• vitest run packages/ai/phala/src/index.test.ts (12 tests)
• tsc -p packages/ai/phala/tsconfig.json --noEmit
• git diff --check

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