fix: resolve CodeQL, Gitleaks, Black, and Standard JS CI failures

- **Security (CodeQL)**: Implemented rate-limiting (authLimiter) on the /change-password route in `backend/routes/auth.js` and ensured necessary imports (Joi, getUserById) are present to satisfy authorization security requirements.
- **Security (Gitleaks)**: Replaced hardcoded test API token with a placeholder in `main.py` and `test_main.py` to resolve secret scanning alerts.
- **Python (Linting)**: Resolved line length violations (>120 chars) in `rag-agentic-dashboard/gen-sentinel-ai-v24.py` by wrapping long strings and applying Black formatting.
- **JavaScript (Style)**: Aligned `rag-agentic-dashboard/server.js` and `script.js` with Standard JS style, fixing mixed logic operators, unused variables, and multiline array ambiguity.
- **HTML (Formatting)**: Standardized HTML attribute quoting (single to double quotes) in the `public/` directory to satisfy strict structural checks.

Verified all core fixes with targeted verification scripts and local linting tools.

Co-authored-by: OneFineStarstuff <87420139+OneFineStarstuff@users.noreply.github.com>

Author: google-labs-jules[bot]