docs(milestone): complete scheduling-streaming (v0.3)

---ci---
project: orca
phase: 3
milestone: v0.3
status: complete
requirements:
  covered: [REQ-022, REQ-030, REQ-032]
  partial: []
---/ci---

v0.3 milestone merged to main. Includes all v0.2 work (P08-P10) that
was previously on the milestone branch but not yet merged to main, plus
the v0.3 completion work (iter.Seq streaming + doctor network/db).

v0.2 phases included: P08 (mTLS), P09 (scheduling), P10 (security scan).
v0.3 phases: P0 (pre-execution), P1 (iter.Seq streaming), P2 (doctor),
P3 (final review+ship).

Total: 40 requirements, all complete. No new go.mod dependencies.
Full test suite passes under -race. gofmt + go vet clean.

internal/certpaths/certpaths.go

@@ -36,3 +36,13 @@ func ServerCertPath() string { return filepath.Join(Dir(), "server.crt") }
 
 // ServerKeyPath returns the path to server.key.
 func ServerKeyPath() string { return filepath.Join(Dir(), "server.key") }
+
+// DBPath returns the path to the orca SQLite database. Honors $ORCA_DB
+// for testability and explicit override; otherwise defaults to
+// ~/.orca/orca.db under the same Dir() as the cert files.
+func DBPath() string {
+	if p := os.Getenv("ORCA_DB"); p != "" {
+		return p
+	}
+	return filepath.Join(Dir(), "orca.db")
+}