* perf: resolve scan/review pipeline performance bottlenecks (P2)

Fix 10 performance issues — all 'repeated work in loops' patterns:

#41 - Pre-compile regex patterns once per rule instead of per line
#5  - Batch DB queries in handle_find_affected_tests (single IN clause)
#13 - Batch symbol fetch for Affected command (single query)
#14 - Prepare SQL statement once outside test-pattern loop
#59 - Early cutoff in secrets scanner when max_findings reached
#70 - Break out of all loops when symbol cap hit per file
#67 - Cache file reads during sibling search in resolver
#3  - Reuse single Tokio runtime for MCP tool calls (static LazyLock)
#22 - Static LazyLock regexes in detect_function_entry
#24 - Single transaction for prune_deleted instead of per-file

Refs #335

* fix(ci): resolve clippy + security audit failures

- clippy: remove redundant borrow in format! arg (llm.rs:456 &user_prompt)
- security: bump anyhow 1.0.102 -> 1.0.103 (RUSTSEC-2026-0190, downcast_mut unsoundness)
- security: bump crossbeam-epoch 0.9.18 -> 0.9.20 (RUSTSEC-2026-0204, fmt::Pointer null deref)

Refs #335

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Co-authored-by: ajianaz <ajianaz@users.noreply.github.com>