Summary

Fixes #14 - Authentication failures when using configured API key with MegaLLM proxy

When a configured API key is set for the Anthropic provider, the passthrough mode was previously sending both the configured x-api-key AND any Authorization header from the client request. This caused authentication failures with some proxies (like MegaLLM) that don't expect both headers.

Changes

• Filter out both authorization and x-api-key headers from client requests when a configured API key is present
• Only use the configured API key for authentication in this case
• Preserve all headers (including client auth) when no API key is configured
• Add debug logging to show filtered headers and final headers sent to Anthropic API
• Applied to both send_passthrough and stream_passthrough methods
• Fix clippy warning in pricing.rs (identity_op)

Affected Components

• crates/lunaroute-egress/src/anthropic.rs - Anthropic egress connector passthrough methods
• crates/lunaroute-ui/src/pricing.rs - Clippy fix

Testing

• ✅ All 403 tests pass
• ✅ Cargo clippy passes with no warnings
• ✅ Cargo build successful

Behavior

Before

Client Request Headers:
  Authorization: Bearer client-token
  x-api-key: client-key

Sent to Anthropic:
  Authorization: Bearer client-token  ❌ (causes conflict)
  x-api-key: configured-key           ✅

After

Client Request Headers:
  Authorization: Bearer client-token
  x-api-key: client-key

Sent to Anthropic:
  x-api-key: configured-key           ✅ (only configured key sent)

When no configured API key exists, all client headers are passed through unchanged (original behavior preserved).

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