Add interactive prompt for configuration file setup (filters & publishing overrides)

Problem

After running apiops init to scaffold the repo and the identity prompt to connect GitHub & Azure, there is no guided experience for setting up configuration files (extraction filters and publishing overrides). Users must manually create and edit these files, which is error-prone and requires deep knowledge of the configuration schema.

Context — Current Onboarding Flow

1. apiops init — scaffolds the repo structure and CI/CD pipelines
2. Identity prompt — connects GitHub & Azure (OIDC, service principals, etc.)
3. First extraction — pulls down the current APIM state into the repo
4. ❌ Missing step — no guided setup for configuration files

Proposed Solution

Add a new interactive prompt (e.g., apiops configure or a post-extraction prompt) that helps users produce well-structured configuration files after their first extraction. The prompt should:

1. Review Extracted Files

• Scan the extracted APIM artifacts to understand what resources exist (APIs, named values, backends, products, etc.)
• Identify resources that commonly need per-environment overrides (e.g., named values with secrets, backend URLs, etc.)

2. Generate Filter Configuration

• Walk the user through which APIs/resources to include or exclude from publishing
• Produce the appropriate filter/extraction configuration file

3. Generate Publishing Override Configuration

• Identify values that likely differ across environments (dev → staging → prod)
• For placeholder/token values needed in production, interactively ask the user for the correct values or secret references
• Generate environment-specific configuration files (e.g., configuration.prod.yaml) with appropriate overrides
• Use {#[TOKEN_NAME]#} placeholder syntax for secrets (per #117)

4. Interactive & Best-Effort

• The prompt should be conversational — guide the user through decisions rather than requiring upfront knowledge
• Make sensible defaults and best-effort suggestions based on the extracted artifacts
• Allow the user to review and confirm before writing files

Acceptance Criteria

• New interactive prompt is available to run after the first extraction
• Prompt scans extracted artifacts and identifies resources needing overrides
• Prompt interactively asks users about environment-specific values (especially secrets/production placeholders)
• Generates filter configuration for extraction
• Generates per-environment publishing override configuration files
• Uses {#[TOKEN_NAME]#} placeholder syntax for secret values
• Provides sensible defaults and best-effort suggestions
• Documentation explains when and how to run this prompt in the onboarding flow