Add DNS query log parser (dnsmasq / Pi-hole)

[copyleftdev]

Implements the DNS query log plugin — issue #19.

What

DNS is a favorite covert channel, so beyond extracting the query, DnsParser
computes the features that expose tunnelling:

• qname_entropy (Shannon entropy of the query name) + qname_length →
  point detection of DGA / exfil names (long, high-entropy);
• timestamp_epoch → cadence on query timing (beaconing);
• qtype (e.g. TXT) and client round out each row.

Parses the dnsmasq query line shape <time> dnsmasq[pid]: query[TYPE] NAME from CLIENT; non-query lines (forwarded / reply / cached / config) produce no rows.
The query type must start with an uppercase letter, ruling out prose like
query[0] x from y.

Determinism

The dnsmasq BSD timestamp has no year, so it's parsed with a fixed sentinel year
in UTC — deterministic, never the wall clock (Jan 1 00:00:00 → epoch 0).

Routing

• Detected by a parseable query line (scanning the first lines, since logs may
  open with non-query lines), STRONG.
• Claims no extension (DNS logs are generically *.log).

Errors

Input with no query lines is a clean AxError::Parse.

Gates

• fmt / clippy -D warnings / full workspace tests green (both feature sets).
• Mutation gate: 0 surviving mutants on dns.rs (entropy, epoch, and
  query-parse logic all covered; the extensions() empty-slice mutant is a
  documented equivalent).
• Smoke: a query log routes as dns; high-entropy DGA/exfil names are flagged by
  point.modz on qname_entropy/qname_length (exit 1).

Closes #19

🤖 Generated with Claude Code

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: e97d02fc-1abb-4571-b949-69413d95fc3e

📥 Commits

Reviewing files that changed from the base of the PR and between 2c1fc9e and 55f25b2.

📒 Files selected for processing (4)

• .cargo/mutants.toml
• crates/ax-normalize/src/parser.rs
• crates/ax-normalize/src/parsers/dns.rs
• crates/ax-normalize/src/parsers/mod.rs

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/dns

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