feat: support per-repository scanner profiles

[edgepillar]

Summary

• add --scanner-config-file support to loupectl repo add and repo update
• persist scanner configuration updates through the protocol, server, and storage layers
• add extra_source_paths to repository source discovery
• allow explicitly selected extensionless operational files such as Dockerfile and Caddyfile
• reject absolute paths, traversal, missing paths, and symlink targets outside the worktree
• document the per-repository scanner profile workflow

Motivation

Repositories can contain security-relevant operational files outside Loupe's automatically discovered package roots. A stored per-repository profile makes that scope explicit and repeatable without discarding existing scan history when the profile changes.

The first prepared consumer is 0x3639/testnet, whose profile adds its devnet setup script, container definitions, Caddy configuration, and Vite configuration to the normal TypeScript source scope.

Validation

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets --all-features -- -D warnings on Linux
• cargo check --workspace --all-targets on Linux
• cargo test --workspace --all-targets on Linux
• cargo test -p loupe-cli -p loupe-proto -p loupe-storage (115 local tests passed)
• source-discovery harness, including the real testnet profile (18 local tests passed)
• git diff --check

Safety

Configured paths are canonicalized and constrained to the checked-out worktree. Invalid, escaping, and missing entries are ignored with a warning. Explicit files still honor path exclusions and size limits.

Privacy

The change contains no credentials, repository secrets, personal identifiers, or local filesystem paths.