matrix: logs only non-sensitive config fields

[l5yth]

Sanitized the Matrix bridge startup log to avoid leaking appservice tokens, and moved Matrix auth to Authorization: Bearer headers on outbound requests while keeping the Synapse listener compatible with legacy query tokens. Updated the related tests to assert header-based auth and added coverage for legacy query and X-Access-Token headers.

• matrix/src/main.rs logs only non-sensitive config fields via a dedicated helper, removing token exposure.
• matrix/src/matrix.rs sends appservice auth via bearer_auth and adjusts mock expectations accordingly.
• matrix/src/matrix_server.rs accepts Authorization: Bearer or X-Access-Token headers with constant-time token comparison and falls back to query params only when headers are missing; tests updated to cover header and legacy paths.

[codecov]

Codecov Report

❌ Patch coverage is 95.58824% with 6 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
matrix/src/matrix_server.rs	92.68%	6 Missing ⚠️

📢 Thoughts on this report? Let us know!