refactor: distribute Acaua as a Docker image instead of a desktop app

Acaua is a collective SOC daemon consuming only Zeek log files, not a
single-user tool needing local hardware like its siblings. Drop the
Tauri desktop shell, installers and self-update entirely; the server
and its web dashboard ship as a container, updated by pulling a new
image tag.

Link against the official prebuilt libduckdb instead of compiling it
from source via the bundled feature, cutting image build time from
15+ minutes to about 3. Fix a real bug found along the way: as PID 1
in a container, the daemon ignored SIGTERM and was always killed
after the stop timeout; it now shuts down gracefully.

Also corrects the Pillar 1 beaconing score: the period estimate had a
harmonic alias (a perfectly periodic 4h series resolved to 600s), and
the old score formula flagged pure random traffic as suspicious
(p95 = 0.839 on Poisson noise). The new formula was validated against
300 samples per scenario.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VAyr8d7HuAdUGB6aA5xmDD

crates/acaua-core/tests/smoke.rs

@@ -7,7 +7,7 @@ fn pillar1_returns_a_skeleton_score() {
     };
     let score = pillar1::score(&input).unwrap();
     assert_eq!(score.observations, 3);
-    assert_eq!(score.status, "skeleton");
+    assert_eq!(score.status, "insufficient_data");
 }
 
 #[test]
@@ -44,7 +44,7 @@ fn fusion_returns_no_alerts_yet() {
 
 #[test]
 fn storage_reports_the_reserved_backend() {
-    let store = storage::Storage::open(std::env::temp_dir());
+    let store = storage::Storage::open(std::env::temp_dir()).unwrap();
     let summary = store.summary().unwrap();
     assert_eq!(summary.ttl_days, 7);
     assert_eq!(summary.records, 0);
@@ -52,7 +52,8 @@ fn storage_reports_the_reserved_backend() {
 
 #[test]
 fn zeek_rejects_a_missing_directory() {
-    let error = zeek::analyze_dir("/definitely/not/a/zeek/directory").unwrap_err();
+    let error =
+        zeek::analyze_dir("/definitely/not/a/zeek/directory", std::env::temp_dir()).unwrap_err();
     assert!(matches!(error, AcauaError::InvalidInput(_)));
 }