cherry-pick #1: initial Kindred branding + assembly joint fix

Cherry-picked 316d4f4b52 with conflict resolution:
- CMakeLists.txt: merged Kindred version vars with upstream 1.2.0-dev base
- src/Main/*.cpp: applied Kindred branding (banner, copyright, license)
- Resolved add/add conflicts for files already copied in Phase 1
- Includes assembly joint flip overconstrain fix

src/Mod/Assembly/App/AssemblyObject.cpp

@@ -165,9 +165,8 @@ int AssemblyObject::solve(bool enableRedo, bool updateJCS)
 
     jointParts(joints);
 
-    if (enableRedo) {
-        savePlacementsForUndo();
-    }
+    // Always save placements to enable orientation flip detection
+    savePlacementsForUndo();
 
     try {
         mbdAssembly->runPreDrag();
@@ -186,8 +185,22 @@ int AssemblyObject::solve(bool enableRedo, bool updateJCS)
         return -1;
     }
 
+    // Validate that the solve didn't cause any parts to flip orientation
+    if (!validateNewPlacements()) {
+        // Restore previous placements - the solve found an invalid configuration
+        undoSolve();
+        lastSolverStatus = -2;
+        updateSolveStatus();
+        return -2;
+    }
+
     setNewPlacements();
 
+    // Clear undo history if the caller didn't want redo capability
+    if (!enableRedo) {
+        clearUndo();
+    }
+
     redrawJointPlacements(joints);
 
     updateSolveStatus();
@@ -480,8 +493,56 @@ bool AssemblyObject::validateNewPlacements()
         }
     }
 
-    // TODO: We could do further tests
-    // For example check if the joints connectors are correctly aligned.
+    // Check if any part has flipped orientation (rotation > 90 degrees from original)
+    // This prevents joints from "breaking" when the solver finds an alternate configuration
+    for (const auto& savedPair : previousPositions) {
+        App::DocumentObject* obj = savedPair.first;
+        if (!obj) {
+            continue;
+        }
+
+        auto it = objectPartMap.find(obj);
+        if (it == objectPartMap.end()) {
+            continue;
+        }
+
+        std::shared_ptr<MbD::ASMTPart> mbdPart = it->second.part;
+        if (!mbdPart) {
+            continue;
+        }
+
+        Base::Placement newPlacement = getMbdPlacement(mbdPart);
+        if (!it->second.offsetPlc.isIdentity()) {
+            newPlacement = newPlacement * it->second.offsetPlc;
+        }
+
+        const Base::Placement& oldPlc = savedPair.second;
+
+        // Calculate the rotation difference between old and new orientations
+        Base::Rotation oldRot = oldPlc.getRotation();
+        Base::Rotation newRot = newPlacement.getRotation();
+
+        // Get the relative rotation: how much did the part rotate?
+        Base::Rotation relativeRot = newRot * oldRot.inverse();
+
+        // Get the angle of this rotation
+        Base::Vector3d axis;
+        double angle;
+        relativeRot.getRawValue(axis, angle);
+
+        // If the part rotated more than 90 degrees, consider it a flip
+        // Use 91 degrees to allow for small numerical errors
+        constexpr double maxAngle = 91.0 * M_PI / 180.0;
+        if (std::abs(angle) > maxAngle) {
+            Base::Console().warning(
+                "Assembly : Ignoring bad solve, part (%s) flipped orientation (%.1f degrees).\n",
+                obj->getFullLabel(),
+                std::abs(angle) * 180.0 / M_PI
+            );
+            return false;
+        }
+    }
+
     return true;
 }