Store and describe images through a shared media intake (#252)

Vision needs a second model this box does not have, so the shipped half is
the part that works without one: an image arrives, is sniffed, is stored
content-addressed, and is prepared for inference. The describing half is
written and tested against a fake server, and refuses any endpoint that is
not on this box.

internal/media is the intake all three senses share — hearing and speaker
recognition store their audio in the same place under the same retention.
Blobs stay out of the sqlite store; only the derived text becomes a note,
and only when the caller asks. Retention is enforced by an hourly prune
loop rather than by a comment.

The plan's RemoteProvider step is refused: no cloud model, inference stays
on the box, and vision.NewLocal validates that at construction.

internal/ipc/server.go

@@ -449,6 +449,16 @@ type Server struct {
 	SwapModelFn   SwapModelFunc
 	ModelStatusFn ModelStatusFunc
 
+	// DescribeImageFn — looks at one image (Vikunja #252). Set by the daemon only
+	// when a media store is configured AND vision is enabled with a local
+	// endpoint; nil ⇒ MethodDescribeImage answers ErrUnknownMethod, so a surface
+	// cannot make Maven accept a photo by merely sending one.
+	//
+	// It bypasses CoreAPI for the same reason IngestMailFn does: it needs a blob
+	// store and a vision server, neither of which is a store operation, and no
+	// other CoreAPI implementation should have to carry it.
+	DescribeImageFn DescribeImageFunc
+
 	// UnlockFn — unwraps the store encryption key from the wrapped blob using
 	// the passkey credential public key, opens the encrypted store, and wires
 	// the rest of the daemon (voice, loop, delivery). Set by the daemon when
@@ -476,6 +486,9 @@ type ModelStatusFunc func(ctx context.Context) (ModelStatusResp, error)
 // IngestMailFunc — core-side mail extraction. Returns what was captured.
 type IngestMailFunc func(ctx context.Context, req IngestMailReq) (IngestMailResp, error)
 
+// DescribeImageFunc — core-side image intake + description.
+type DescribeImageFunc func(ctx context.Context, req DescribeImageReq) (DescribeImageResp, error)
+
 // CheckFunc — the auth hook signature. Wired by the daemon (auth.Gate.Check
 // satisfies this); dispatch calls it once per request after param-unmarshal
 // independence (it gets the raw params, may unmarshal what it needs — ipc
@@ -644,10 +657,10 @@ func withoutParams[R any](fn func(ctx context.Context, api CoreAPI) (R, error))
 // is still honored on the very next request with no extra plumbing here.
 //
 // MethodAssertStepUp, MethodStoreEncryptionKey, MethodUnlock,
-// MethodIngestMail, MethodSwapModel and MethodModelStatus are NOT in this
-// table: they bypass CoreAPI entirely
-// (s.StepUp / s.WrapKeyFn / s.UnlockFn / s.IngestMailFn), so dispatch
-// special-cases them before consulting the table.
+// MethodIngestMail, MethodSwapModel, MethodModelStatus and
+// MethodDescribeImage are NOT in this table: they bypass CoreAPI entirely
+// (s.StepUp / s.WrapKeyFn / s.UnlockFn / s.IngestMailFn / s.DescribeImageFn),
+// so dispatch special-cases them before consulting the table.
 var methodTable = map[Method]handlerFunc{
 	MethodWriteFact: withParams(func(ctx context.Context, api CoreAPI, p WriteFactReq) (idResp, error) {
 		id, err := api.WriteFact(ctx, p)
@@ -923,6 +936,20 @@ func (s *Server) dispatch(ctx context.Context, req Request) (json.RawMessage, er
 		}
 		return nil, fmt.Errorf("%w: %s", ErrUnknownMethod, req.Method)
 
+	case MethodDescribeImage:
+		if s.DescribeImageFn != nil {
+			var p DescribeImageReq
+			if err := unmarshalParams(req.Params, &p); err != nil {
+				return nil, err
+			}
+			resp, err := s.DescribeImageFn(ctx, p)
+			if err != nil {
+				return nil, err
+			}
+			return marshalResult(resp), nil
+		}
+		return nil, fmt.Errorf("%w: %s", ErrUnknownMethod, req.Method)
+
 	case MethodModelStatus:
 		if s.ModelStatusFn != nil {
 			resp, err := s.ModelStatusFn(ctx)