feat: make Argon2 parameters configurable for faster test execution

[fergusfinn]

This change makes Argon2 password hashing parameters (memory, iterations, parallelism) configurable through PasswordConfig, with weak defaults in test environments for dramatically faster test execution.

Performance Impact

Auth test suite with coverage:

• Before (19MB, 2 iter): 15.38s
• After (128KB, 1 iter): 0.67s

This resolves the issue where cargo llvm-cov was significantly slower than cargo test (i think?) due to instrumenting Argon2's internal hashing loops.

[railway-app]

🚅 Environment control-layer-pr-239 in industrious-light has no services deployed.

[Copilot]

@fergusfinn I've opened a new pull request, #240, to work on those changes. Once the pull request is ready, I'll request review from you.

[Copilot]

Pull request overview

This PR introduces configurable Argon2 password hashing parameters to dramatically improve test execution speed while maintaining secure defaults for production. The test suite now runs in 0.67s (down from 15.38s) by using weak hashing parameters (128KB memory, 1 iteration) instead of production defaults (19MB, 2 iterations).

Key changes:

• Added three configurable Argon2 parameters to PasswordConfig: argon2_memory_kib, argon2_iterations, and argon2_parallelism
• Introduced Argon2Params struct and hash_string_with_params function for explicit parameter control
• Updated all password hashing call sites to pass configuration-based parameters

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
dwctl/src/auth/password.rs	Adds Argon2Params struct and parameterized hashing functions, maintaining backward compatibility with hash_string()
dwctl/src/config.rs	Extends PasswordConfig with Argon2 parameters using secure production defaults (19MB, 2 iterations)
dwctl/src/test_utils.rs	Configures weak Argon2 parameters (128KB, 1 iteration) for fast test execution
dwctl/src/lib.rs	Updates create_initial_admin_user to accept Argon2Params and use config values; updates test calls with weak params
dwctl/src/api/handlers/auth.rs	Extracts Argon2 params from config in registration, password reset, and password change handlers; updates all test fixtures with weak params
dwctl/src/db/models/password_reset_tokens.rs	Adds argon2_params field to PasswordResetTokenCreateRequest for token hashing
dwctl/src/db/handlers/password_reset_tokens.rs	Passes Argon2 params from config when creating password reset tokens

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[Copilot]

@fergusfinn I've opened a new pull request, #241, to work on those changes. Once the pull request is ready, I'll request review from you.