Add Trakt client_id/secret/redirect_uri to server-settings schema

[detain]

Adds the three Trakt.tv operator-credential keys to the shared server-settings schema so phlix-server's admin Settings UI can render fields for them (the in-app half of the agreed "Both" approach for configuring Trakt; env-var support already shipped on the server in phlix-server#196).

New keys (group scrobblers, all string):

• trakt.client_id
• trakt.client_secret
• trakt.redirect_uri

Additive and backward-compatible (runtime defaults still live in phlix-server config/*.php, per the schema's own contract). ServerSettingsSchemaTest updated to expect 18 keys (was 15). Full suite (289) + phpstan green.

Consumed by phlix-server via composer update detain/phlix-shared in a follow-up PR that adds the Settings form fields and makes TraktOAuthController read these from server_settings (DB) with precedence over env/file.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 53.22%. Comparing base (afc91d8) to head (9a47599).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master       #9   +/-   ##
=========================================
  Coverage     53.22%   53.22%           
  Complexity      353      353           
=========================================
  Files            34       34           
  Lines          1084     1084           
=========================================
  Hits            577      577           
  Misses          507      507           

Flag	Coverage Δ
phpunit	53.22% <ø> (ø)

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[codacy-production]

Not up to standards ⛔

🔴 Issues 1 minor

Alerts:
⚠ 1 issue (≤ 0 issues of at least minor severity)

Results:
1 new issue

Category	Results
CodeStyle	1 minor

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🟢 Metrics 0 complexity · 0 duplication

Metric	Results
Complexity	0
Duplication	0

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