Import: bring a HAR file's entries into history

Closes the interop loop HAR export opened - traffic can now move both
directions between mitmux and any other HAR-producing tool (browser
DevTools, Burp, Postman), not just out.

cmd/mitmux/har.go: rawRequestFromHAR/rawResponseFromHAR reconstruct
HTTP/1.1 wire bytes from HAR's structured fields - the mirror image of
harEntryFromDetail on the export side. Deliberately tolerant of a HAR
file that didn't come from mitmux at all: lowercase header names,
"HTTP/2" in httpVersion, missing optional fields like postData, a
redirectURL nobody filled in. Content-Encoding and Transfer-Encoding
headers are stripped from the reconstructed response before writing it
- HAR's content.text is already decoded per spec, so re-emitting those
headers would describe framing the body no longer has and break any
client that tried to decode it again - and a Content-Length is computed
if the HAR didn't carry a consistent one. importEntriesFromHAR converts
a whole document, skipping (not failing on) any entry that fails to
convert, same reasoning as export's own skip-and-continue for a
malformed capture.

Imported entries are always request_exact=false/response_exact=false:
reconstructed from structured HAR fields, the same situation an HTTP/2
capture is already in, never claiming to be the literal bytes that were
actually on the wire for the original request.

internal/ipc: ImportEntry (the slim shape the client sends - the daemon
just stores what it's given, all HAR parsing happens client-side) and
an "import" request type; Client.Import returns how many entries were
actually inserted, a per-entry store failure is skipped rather than
aborting the batch. Server-side, imported entries are tagged
source="import" so source:import finds them in search, same as
source:repeater/source:intruder already work.

TUI: 'I' from the history list prompts for a HAR path (same modal
pattern as export, in reverse - reading instead of writing), then
reloads the list and status once the import completes.

Verified live: exported real captured traffic to HAR, cleared history
entirely, imported the same file back and got both entries with
correct content (byte-different after the round trip - headers get
reordered/reformatted - but semantically identical, correctly labeled
"reconstructed" rather than falsely "exact"); hand-built a HAR mimicking
a real Chrome DevTools export (lowercase headers, HTTP/2, a base64-
encoded binary PNG body, several optional fields omitted) and confirmed
it imports cleanly with the binary body decoded correctly (PNG magic
bytes verified byte-for-byte); confirmed a missing file and invalid
JSON both fail with a clear error and no crash, history left untouched.

go build/vet/gofmt/test/mod tidy all clean.

1 files changed, 21 insertions, 0 deletions

diff --git a/internal/ipc/server.go b/internal/ipc/server.go
index 303fdef..c83254e 100644
--- a/internal/ipc/server.go
+++ b/internal/ipc/server.go
@@ -230,6 +230,27 @@ func (s *Server) handleConn(conn net.Conn) {
 			}
 			enc.Encode(Response{Type: "cleared"})
 
+		case "import":
+			imported := 0
+			for _, ie := range req.ImportEntries {
+				e := &store.Entry{
+					StartedAt:   ie.StartedAt,
+					Duration:    ie.Duration,
+					Method:      ie.Method,
+					Scheme:      ie.Scheme,
+					Host:        ie.Host,
+					Path:        ie.Path,
+					StatusCode:  ie.StatusCode,
+					RequestRaw:  ie.RequestRaw,
+					ResponseRaw: ie.ResponseRaw,
+					Source:      "import",
+				}
+				if _, err := s.db.Insert(e); err == nil {
+					imported++
+				}
+			}
+			enc.Encode(Response{Type: "import_done", Imported: imported})
+
 		case "rules_list":
 			rs, err := s.db.ListRules()
 			if err != nil {