Track the real script in the credentials xcfilelist

The declared input was `ApplyConfiguration.sh`, which no longer exists.
Xcode cannot stat a missing input, so the phase re-ran on every build and
editing `GenerateCredentials.sh` never invalidated it — the opposite of what the
comment above the line promises.

Safe to fix only now that each target writes to its own `DERIVED_FILE_DIR`.
While the three app targets shared one output path, the perpetual re-run was
what kept them from compiling each other's secrets.

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Generated with the help of Claude Code, https://claude.com/claude-code

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: mokagio

Scripts/BuildPhases/GenerateCredentials.xcfilelist

@@ -18,4 +18,4 @@ ${SRCROOT}/Credentials/Secrets-example.swift
 
 # Add the script that uses this file as a source, so that, if the script
 # changes, Xcode will run it again on the next build.
-${SRCROOT}/../Scripts/BuildPhases/ApplyConfiguration.sh
+${SRCROOT}/../Scripts/BuildPhases/GenerateCredentials.sh